Refills prescriptions and Tranferring Prescriptions. How should I approach this? - asp.net

Question

I have some doubts I would like to clear.
We have two features on our website we would like to provide to our customers for dealing with prescription drugs.
One feature allows potential new customers to transfer their prescription drugs from their current providing pharmacy to our pharmacy.
Another feature allows current customers to refill their current prescriptions.
Prescriptions must be either transferred from previous provider or must have existed before they can refilled.
To achieve the prescription transfer portion, I have two tables, one called Customer (which contains customer personal info as well as current providing pharmacy name and phone number) and the other called Prescriptions. This table contains prescription info. customerId is on this table as Foreign key to customer table.
The code below inserts records into customer table and prescriptions table for customers transferring their prescriptions from one pharmacy to our pharmacy.
I am also aware that I need to perform a check to see if customer trying to transfer prescriptiosn already exists on our table. I have not done this yet but will.
My doubt is how to handle the Refill portion of this task.
Any ideas is greatly appreciated.
Here is the code that inserts Transferred prescriptions.
Protected Sub btnSave_Click(ByVal sender As Object, ByVal e As EventArgs)
Dim s As String
Dim sql As String
Dim connStr As String = "Provider=Microsoft.ACE.OLEDB.12.0;data source=" & Server.MapPath("App_Data\GCP.accdb")
Try
SetRowData()
Dim table As DataTable = TryCast(ViewState("CurrentTable"), DataTable)
If table IsNot Nothing Then
s = "INSERT INTO Customer(FirstName, LastName, MiddleInitial, DOB, Email_Address, Phone, Address, City, State, ZipCode, PharmacyName, PharmacyPhone) Values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)"
sql = "Select Max(custId) From Customer"
'Response.Write(s)
'Response.End()
Dim con As New OleDbConnection(connStr)
Dim cmd1 As New OleDbCommand(s, con)
cmd1.Parameters.AddWithValue("", txtfName.Text)
cmd1.Parameters.AddWithValue("", txtMI.Text)
cmd1.Parameters.AddWithValue("", txtLName.Text)
cmd1.Parameters.AddWithValue("", txtDOB.Text)
cmd1.Parameters.AddWithValue("", txtemail.Text)
cmd1.Parameters.AddWithValue("", txtphone.Text)
cmd1.Parameters.AddWithValue("", txtAddress.Text)
cmd1.Parameters.AddWithValue("", txtcity.Text)
cmd1.Parameters.AddWithValue("", txtstate.Text)
cmd1.Parameters.AddWithValue("", txtzip.Text)
cmd1.Parameters.AddWithValue("", txtpharmacyName.Text)
cmd1.Parameters.AddWithValue("", txtPharmacyPhone.Text)
con.Open()
cmd1.ExecuteNonQuery()
cmd1.CommandText = sql
ID = cmd1.ExecuteScalar()
For Each row As DataRow In table.Rows
Dim txPrescription As String = TryCast(row.ItemArray(1), String)
If txPrescription IsNot Nothing Then
Try
s = "INSERT INTO Prescriptions(Prescription, custId) VALUES "
s += "('" & txPrescription & "', " & ID & ")"
'Response.Write(s)
'Response.End()
'Dim connStr As String = ConfigurationManager.ConnectionStrings("allstringconstrng").ConnectionString
Dim conn As New OleDbConnection(connStr)
Dim cmd As New OleDbCommand(s, conn)
conn.Open()
cmd.ExecuteNonQuery()
conn.Close()
'Display some feedback to the user to let them know it was processed
lblResult.ForeColor = System.Drawing.Color.Green
lblResult.Text = "Your Prescriptions Transfer Request has been sent. Prescription requests are normally processed within 24 hours!"
'Clear the form
txPrescription = ""
txtfName.Text = ""
txtMI.Text = ""
txtLName.Text = ""
txtDOB.Text = ""
txtemail.Text = ""
txtphone.Text = ""
txtAddress.Text = ""
txtcity.Text = ""
txtstate.Text = ""
txtzip.Text = ""
Catch
'If the message failed at some point, let the user know
lblResult.ForeColor = System.Drawing.Color.Red
lblResult.Text = "Your record failed to save, please try again."
End Try
End If
Next
End If
Catch ex As Exception
Throw New Exception(ex.Message)
End Try
End Sub