You have default form when project opens. In that form's Open event:
Code:
Private Sub Form_Open(Cancel As Integer)
Dim x As Integer
x = DCount("[DebtorID3]", "[cust test]", "[PROOF OF CLAIM FILING DATE]+30>=" & Date)
If x > 0 Then
MsgBox x & " Proof of Claim due."
End If
End Sub
Instead of message box, could have a query, form, or report open.
You have a subform to show account info. That subform's RecordSource does not need to be a join of tables. This is causing confusion. The Master/Child links are wrong. Need to be DebtorID and DebtorID3. The subform is set to Single record view. If you want to see all accounts for the client then set to Continuous or Datasheet view and reduce the size of the textbox and the Detail section.