Suspect code running twice or not at all sometimes, intermittent issue - asp.net

Question

The code below is causing me some real headaches. It was written probably two years ago and has been chugging away ever since, but we've noticed that sometimes the insert query will run twice, and sometimes not at all. The code basically takes integer and decimal values from webpage (aspx) labels and inserts them into a master table.
The problem lately seems to be affected by the number of users on the system. When there is only one person using it there seems to be no issue, but with multiple users the problems start to occur. I was using session variables rather than labels but as a process of elimination i stopped using these.
If anyone can help or give me some pointers that would be great, many thanks.
Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSubmit.Click
'local
Dim subidString As String = "SELECT [Submission_ID], [Week Ending] FROM tbl_Weekly_Expenses WHERE [Submission_ID] = #SubID AND [Week Ending] = #WeekEnding AND [SentToPayroll] IS NULL"
'local
Dim mtdString As String = "SELECT SUM([Mileage Covered]) AS SumOfMileageCovered FROM tbl_Weekly_Expenses WHERE [Gabem Employee Reference] = #NovaRef"
'remote
Dim vehicleString As String = "SELECT [Vehicle] FROM tblExpensesMileage WHERE [SubID] = #SubID"
'local
Dim insertString As String = "INSERT INTO tbl_Weekly_Expenses ([Week Ending], [Date Expenses Processed], [Expenses_From], [Expenses_To], [Date Expenses received], [Gabem Employee Reference], [Identifying Number], [Submission_ID], [Car], [Motorcycle], [Pushbike], [Mileage Covered], [Mileage Amount Claimed], [Accommodation], [Meal Allowance], [Daily Allowance], [Tools/Clothing], [Details_Of_Tools], [Travel Amount], [Telephone], [Professional Fees], FuelVAT, MAVAT, TAVAT, AVAT, DAVAT, TCVAT, TelVAT, PfVAT, processedby) " & _
"VALUES (#WeekEnding, #DateProcessed, #ExpensesFrom, #ExpensesTo, #DateReceived, #NovaRef, #IdentifyingNumber, #SubID, #Car, #Motorcycle, #Pushbike, #MileageCovered, #MileageAmountClaimed, #Accommodation, #Meals, #DailyAllowance, #ToolsClothing, #ToolsDetails, #Travel, #TelephoneCalls, #ProfessionalFees, #FuelVAT, #MAVAT, #TAVAT, #AVAT, #DAVAT, #TCVAT, #TelVAT, #PfVAT, #processedby)"
'remote
Dim updateMileage As String = "UPDATE tblExpensesMileage SET [Status] = 'Processed' WHERE [MileageID] = #id"
Dim updateAccommodation As String = "UPDATE tblExpensesAccommodation SET [Status] = 'Processed' WHERE [AccommodationID] = #id"
Dim updateMeals As String = "UPDATE tblExpensesMeals SET [Status] = 'Processed' WHERE [MealsID] = #id"
Dim updateLaundry As String = "UPDATE tblExpensesLaundry SET [Status] = 'Processed' WHERE [LaundryID] = #id"
Dim updateDailyAllowance As String = "UPDATE tblExpensesDailyAllowance SET [Status] = 'Processed' WHERE [DailyAllowanceID] = #id"
Dim updateTravel As String = "UPDATE tblExpensesTravel SET [Status] = 'Processed' WHERE [TravelID] = #id"
Dim updateTools As String = "UPDATE tblExpensesTools SET [Status] = 'Processed' WHERE [ToolsID] = #id"
Dim updateTelephoneCalls As String = "UPDATE tblExpensesTelephoneCalls SET [Status] = 'Processed' WHERE [TelephoneCallsID] = #id"
Dim updateProfessionalFees As String = "UPDATE tblExpensesProfessionalFees SET [Status] = 'Processed' WHERE [ProfessionalFeesID] = #id"
Dim dbconnLocal As String = ConfigurationManager.ConnectionStrings("connection_nbsas2").ConnectionString
Dim dbconnRemote As String = ConfigurationManager.ConnectionStrings("connection_nbsa_web").ConnectionString
If txtWEDate.Text = String.Empty Then
Exit Sub
End If
Using myConnectionLocal As New SqlConnection(dbconnLocal)
myConnectionLocal.Open()
'VEHICLE TYPE AND PPM STARTS
Dim Car As Integer = 0
Dim Motorcycle As Integer = 0
Dim Pushbike As Integer = 0
Dim ppm As Decimal
Using myConnectionRemote As New SqlConnection(dbconnRemote)
myConnectionRemote.Open()
'Vehicle type
Dim cmdSelectVehicle As New SqlCommand(vehicleString, myConnectionRemote)
cmdSelectVehicle.Parameters.AddWithValue("#SubID", Session("subid"))
Dim readerVehicle As SqlDataReader = cmdSelectVehicle.ExecuteReader()
readerVehicle.Read()
If readerVehicle.HasRows = True Then
'MTD value for pence per mile (ppm)
Dim cmdSelectMTD As New SqlCommand(mtdString, myConnectionLocal)
cmdSelectMTD.Parameters.AddWithValue("#NovaRef", Session("novaref"))
Dim readerMTD As SqlDataReader = cmdSelectMTD.ExecuteReader()
readerMTD.Read()
If IsDBNull(readerMTD.Item(0)) = True Then
If readerVehicle.Item(0) = "Car" Then
ppm = 0.45
Car = "1"
ElseIf readerVehicle.Item(0) = "Motorcycle" Then
ppm = 0.24
Motorcycle = "1"
Else
ppm = 0.2
Pushbike = "1"
End If
Else
If readerVehicle.Item(0) = "Motorcycle" Then
ppm = 0.24
Motorcycle = "1"
ElseIf readerVehicle.Item(0) = "Car" And readerMTD.Item(0) < 10000 Then
ppm = 0.45
Car = "1"
ElseIf readerVehicle.Item(0) = "Car" And readerMTD.Item(0) > 10000 Then
ppm = 0.25
Car = "1"
Else
ppm = 0.2
Pushbike = "1"
End If
End If
readerMTD.Close()
End If
readerVehicle.Close()
myConnectionRemote.Close()
End Using
'VEHICLE TYPE AND PPM ENDS
'insert parameters etc
Dim cmdInsertWE As New SqlCommand(insertString, myConnectionLocal)
cmdInsertWE.Parameters.AddWithValue("#WeekEnding", CType(txtWEDate.Text, DateTime))
cmdInsertWE.Parameters.AddWithValue("#DateProcessed", Now())
cmdInsertWE.Parameters.AddWithValue("#ExpensesFrom", CType(lblMinDate.Text, DateTime))
cmdInsertWE.Parameters.AddWithValue("#ExpensesTo", CType(lblMaxDate.Text, DateTime))
cmdInsertWE.Parameters.AddWithValue("#DateReceived", CType(Session("daterec"), DateTime))
cmdInsertWE.Parameters.AddWithValue("#NovaRef", Session("novaref"))
cmdInsertWE.Parameters.AddWithValue("#IdentifyingNumber", "1")
cmdInsertWE.Parameters.AddWithValue("#SubID", Session("subid"))
cmdInsertWE.Parameters.AddWithValue("#Car", Car)
cmdInsertWE.Parameters.AddWithValue("#Motorcycle", Motorcycle)
cmdInsertWE.Parameters.AddWithValue("#Pushbike", Pushbike)
cmdInsertWE.Parameters.AddWithValue("#MileageCovered", CType(lblMileageNumber.Text, Decimal))
cmdInsertWE.Parameters.AddWithValue("#MileageAmountClaimed", CType(lblMileageNumber.Text, Decimal) * ppm)
cmdInsertWE.Parameters.AddWithValue("#Accommodation", CType(lblAccommodationNumber.Text, Decimal))
cmdInsertWE.Parameters.AddWithValue("#Meals", CType(lblMealsNumber.Text, Decimal))
cmdInsertWE.Parameters.AddWithValue("#DailyAllowance", CType(lblDailyAllowanceNumber.Text, Decimal))
cmdInsertWE.Parameters.AddWithValue("#ToolsClothing", CType(lblToolsNumber.Text, Decimal) + CType(lblLaundryNumber.Text, Decimal))
cmdInsertWE.Parameters.AddWithValue("#ToolsDetails", txtToolsDetails.Text)
cmdInsertWE.Parameters.AddWithValue("#Travel", CType(lblTravelNumber.Text, Decimal))
cmdInsertWE.Parameters.AddWithValue("#TelephoneCalls", CType(lblTelephoneCallsNumber.Text, Decimal))
cmdInsertWE.Parameters.AddWithValue("#ProfessionalFees", CType(lblProfessionalFeesNumber.Text, Decimal))
cmdInsertWE.Parameters.AddWithValue("#FuelVAT", CType(txtRec_Mileage.Text, Decimal))
cmdInsertWE.Parameters.AddWithValue("#MAVAT", CType(txtRec_Meals.Text, Decimal))
cmdInsertWE.Parameters.AddWithValue("#TAVAT", CType(txtRec_Travel.Text, Decimal))
cmdInsertWE.Parameters.AddWithValue("#AVAT", CType(txtRec_Accommodation.Text, Decimal))
cmdInsertWE.Parameters.AddWithValue("#DAVAT", CType(txtRec_Daily.Text, Decimal))
cmdInsertWE.Parameters.AddWithValue("#TCVAT", CType(txtRec_ToolsLaundry.Text, Decimal))
cmdInsertWE.Parameters.AddWithValue("#TelVAT", CType(txtRec_Telephone.Text, Decimal))
cmdInsertWE.Parameters.AddWithValue("#PfVAT", CType(txtRec_ProFees.Text, Decimal))
cmdInsertWE.Parameters.AddWithValue("#processedby", Page.User.Identity.Name)
cmdInsertWE.ExecuteNonQuery()
cmdInsertWE.Dispose()
myConnectionLocal.Close()
'also clear totals labels
lblMileageNumber.Text = 0
lblAccommodationNumber.Text = 0
lblMealsNumber.Text = 0
lblLaundryNumber.Text = 0
lblDailyAllowanceNumber.Text = 0
lblTravelNumber.Text = 0
lblToolsNumber.Text = 0
txtToolsDetails.Text = String.Empty
lblTelephoneCallsNumber.Text = 0
lblProfessionalFeesNumber.Text = 0
End Using 'myConnectionLocal ENDS
'OPEN REMOTE CONNECTION AND UPDATE STATUS OF LIVE TABLES
Using myConnectionRemote As New SqlConnection(dbconnRemote)
myConnectionRemote.Open()
'Mileage()
updateCheckBoxes(MileageGridView, "MileageHeaderCheckBox", "MileageCheckBox", updateMileage, myConnectionRemote, lblMileageNumber)
'Accommodation()
updateCheckBoxes(AccommodationGridView, "AccommodationHeaderCheckBox", "AccommodationCheckBox", updateAccommodation, myConnectionRemote, lblAccommodationNumber)
'Meals()
updateCheckBoxes(MealsGridView, "MealsHeaderCheckBox", "MealsCheckBox", updateMeals, myConnectionRemote, lblMealsNumber)
'Laundry()
updateCheckBoxes(LaundryGridView, "LaundryHeaderCheckBox", "LaundryCheckBox", updateLaundry, myConnectionRemote, lblLaundryNumber)
'Daily(Allowance)
updateCheckBoxes(DailyAllowanceGridView, "DailyAllowanceHeaderCheckBox", "DailyAllowanceCheckBox", updateDailyAllowance, myConnectionRemote, lblDailyAllowanceNumber)
'Travel()
updateCheckBoxes(TravelGridView, "TravelHeaderCheckBox", "TravelCheckBox", updateTravel, myConnectionRemote, lblTravelNumber)
'Tools()
updateCheckBoxes(ToolsGridView, "ToolsHeaderCheckBox", "ToolsCheckBox", updateTools, myConnectionRemote, lblToolsNumber)
'Telephone(Calls)
updateCheckBoxes(TelephoneCallsGridView, "TelephoneCallsHeaderCheckBox", "TelephoneCallsCheckBox", updateTelephoneCalls, myConnectionRemote, lblTelephoneCallsNumber)
'Professional(Fees)
updateCheckBoxes(ProfessionalFeesGridView, "ProfessionalFeesHeaderCheckBox", "ProfessionalFeesCheckBox", updateProfessionalFees, myConnectionRemote, lblProfessionalFeesNumber)
myConnectionRemote.Close()
End Using 'myConnectionRemote ENDS
txtWEDate.Text = String.Empty
End Sub