Audit trail code not picking up combobox list changes - vba

Question

I have looked at this post: Saving changes to a multivalued ComboBox via AuditTrail
And tried to take tidbits and put it into my code, but it just didn't work! I am not really great at SQL but I need to get this done. Here is my code and it works for textboxes, but can someone tell me exactly where and exactly what to put what I need for my combobox dropdown list changes?
Thanks in advance!!
Function LogChanges(lngID As Long, Optional strField As String = "")
Dim dbs As DAO.Database
Dim rst As DAO.Recordset
Dim varOld As Variant
Dim varNew As Variant
Dim strFormName As String
Dim strControlName As String
varOld = Screen.ActiveControl.OldValue
varNew = Screen.ActiveControl.Value
strFormName = Screen.ActiveForm.NAME
strControlName = Screen.ActiveControl.NAME
Set dbs = CurrentDb()
Set rst = dbs.TableDefs("ztblDataChanges").OpenRecordset
With rst
.AddNew
!FormName = strFormName
!ControlName = strControlName
If strField = "" Then
!FieldName = strControlName
Else
!FieldName = strField
End If
!RecordID = lngID
!UserName = Environ("username")
If Not IsNull(varOld) Then
!OldValue = CStr(varOld)
End If
!NewValue = CStr(varNew)
.Update
End With
'clean up
rst.Close
Set rst = Nothing
dbs.Close
Set dbs = Nothing
End Function

Answer 1

You can't get the values of multi-valued fields using .Value and .OldValue. These properties always return Null. As far as I know, there's no reliable way to get the old value (also, a proper audit trail doesn't need an old value, since the old value is the previously added new value if everything gets audited properly).
When only saving the new values, and if you're saving them into a text field and not a multivalued field, you could use the following:
Use this function to get a string value for all selected items:
Public Function JoinMVF(MVFControl As Control, Optional Delimiter As String) As String
Dim i As Variant
For Each i In MVFControl.ItemsSelected
JoinMVF = JoinMVF & MVFControl.ItemData(i) & Delimiter
Next i
End Function
And then, adjust your recordset piece to the following:
With rst
.AddNew
!FormName = strFormName
!ControlName = strControlName
If strField = "" Then
!FieldName = strControlName
Else
!FieldName = strField
End If
!RecordID = lngID
!UserName = Environ("username")
If Not IsNull(varOld) Then 'varOld will always be Null for a multi-valued field
!OldValue = CStr(varOld) 'Thus this will never get called
End If
'Add some If multivalued field then
!NewValue = JoinMVF(Screen.ActiveControl, "; ")
.Update
End With