Tracking value changes when editing a record in Access - ms-access

Question

I am trying to track value changes when editing a record. All fields on the form are unbound text box.
Below is a function that is used to insert a audit tracking record.
Public Function AuditChanges(RecordID As String, UserAction As String)
Dim DB As Database
Dim rst As Recordset
Dim clt As Control
Dim Userlogin As String
Set DB = CurrentDb
Set rst = DB.OpenRecordset("select * from tbl_audittrail", adOpenDynamic)
Userlogin = Environ("username")
Select Case UserAction
Case "Edit"
For Each clt In Screen.ActiveForm.Controls
If (clt.ControlType = acTextBox _
Or clt.ControlType = accombox) Then
If Nz(clt.Value) <> Nz(clt.OldValue) Then
With rst
.AddNew
![DateTime] = Now()
!UserName = Userlogin
!FormName = Screen.ActiveForm.Name
!Action = UserAction
!RecordID = Screen.ActiveForm.Controls(RecordID).Value
!FieldName = clt.ControlSource
!OldValue = clt.OldValue
!Newvalue = clt.Value
.Update
End With
End If
End If
Next clt
End Select
rst.Close
DB.Close
Set rst = Nothing
Set DB = Nothing
End Function
Below is how I use the function:
Private Sub btnUpdate_Click()
Set DB = CurrentDb
Set rs = DB.OpenRecordset("SELECT * FROM ASID", dbOpenDynaset, dbSeeChanges)
rs.Edit
rs!ISIN = Me.ISIN
rs!SECIDTYPE = Me.SECIDTYPE
rs!ALTSECID = Me.ALTSECID
rs.Update
Call AuditChanges("ISIN", "Edit")
End If
End Sub
The problem is when it calls AuditChanges, it goes directly from
If (clt.ControlType = acTextBox _
Or clt.ControlType = accombox)
to End If
All fields on current form are unbound text boxes and you have to press an "Add" command button to actually add a record. I think there must be something wrong with the control type but I am not sure which control type should be used. Any idea?

Answer 1

Start by putting Option Explicit at the top of each module.
It enforces variable declaration and reports undeclared or misspelled variables/constants at compile time.
To have this automatically in new modules, set the Require Variable Declaration option in the VBA Editor.
This is really a must have for VBA development.
Then the compiler will tell you that accombox doesn't exist, it should be acComboBox
Without Option Explicit, accombox is initialized as NULL variant, and causes your entire If condition to be NULL, and therefore never be entered.