Updating existing fields in MS Access database through classic ASP - asp-classic

Question

I've been given working ASP code which I have to change in order to update existing data in database insted of creating new entries. I think I should swap INSERT INTO statment with UPDATE but the code is a bit too coplicated for me to figure out where and what to change.
Here it comes:
// *** Edit Operations: declare variables
// set the form action variable
var MM_editAction = Request.ServerVariables("SCRIPT_NAME");
if (Request.QueryString) {
MM_editAction += "?" + Server.HTMLEncode(Request.QueryString);
}
// boolean to abort record edit
var MM_abortEdit = false;
// query string to execute
var MM_editQuery = "";
// *** Insert Record: set variables
if (String(Request("MM_insert")) == "AddRecord") {
var MM_editConnection = MM_PhoneWeb_conn_STRING;
var MM_editTable = "Employees";
var MM_editRedirectUrl = "userRegister.asp";
var MM_fieldsStr = "textSurname|value|textFirstname|value|textUsername|value|textPass|value";
var MM_columnsStr = "Surname|',none,''|FirstName|',none,''|Username|',none,''|Password|',none,''";
// create the MM_fields and MM_columns arrays
var MM_fields = MM_fieldsStr.split("|");
var MM_columns = MM_columnsStr.split("|");
// set the form values
for (var i=0; i+1 < MM_fields.length; i+=2) {
MM_fields[i+1] = String(Request.Form(MM_fields[i]));
}
// append the query string to the redirect URL
if (MM_editRedirectUrl && Request.QueryString && Request.QueryString.Count > 0) {
MM_editRedirectUrl += ((MM_editRedirectUrl.indexOf('?') == -1)?"?":"&") + Request.QueryString;
}
}
// *** Insert Record: construct a sql insert statement and execute it
if (String(Request("MM_insert")) != "undefined") {
// create the sql insert statement
var MM_tableValues = "", MM_dbValues = "";
for (var i=0; i+1 < MM_fields.length; i+=2) {
var formVal = MM_fields[i+1];
var MM_typesArray = MM_columns[i+1].split(",");
var delim = (MM_typesArray[0] != "none") ? MM_typesArray[0] : "";
var altVal = (MM_typesArray[1] != "none") ? MM_typesArray[1] : "";
var emptyVal = (MM_typesArray[2] != "none") ? MM_typesArray[2] : "";
if (formVal == "" || formVal == "undefined") {
formVal = emptyVal;
} else {
if (altVal != "") {
formVal = altVal;
} else if (delim == "'") { // escape quotes
formVal = "'" + formVal.replace(/'/g,"''") + "'";
} else {
formVal = delim + formVal + delim;
}
}
MM_tableValues += ((i != 0) ? "," : "") + MM_columns[i];
MM_dbValues += ((i != 0) ? "," : "") + formVal;
}
MM_editQuery = "insert into " + MM_editTable + " (" + MM_tableValues + ") values (" + MM_dbValues + ")";
if (!MM_abortEdit) {
// execute the insert
var MM_editCmd = Server.CreateObject('ADODB.Command');
MM_editCmd.ActiveConnection = MM_editConnection;
MM_editCmd.CommandText = MM_editQuery;
MM_editCmd.Execute();
MM_editCmd.ActiveConnection.Close();
if (MM_editRedirectUrl) {
Response.Redirect(MM_editRedirectUrl);