AuditTrail Not Working On Sub Forms?

I use the following module to run an audit trail on my database, which is then linked on to the form by using the following code on the BeforeUpdate property of the form. This works perfectly on the form itself - and in tabs - until I am using a subform. How can I get the module to work without having to name each subform (this form uses 3 SFs!)?

Code:
Sub PropertyAuditChanges(IDField As String)
On Error GoTo PropertyAuditChanges_Err
Dim cnn As ADODB.Connection
Dim rst As ADODB.Recordset
Dim ctl As Control
Dim datTimeCheck As Date
Dim strUserID As String
Set cnn = CurrentProject.Connection

[code]....