Forms :: Change Button Enabled Status On Field Values

I have several buttons on a form and I want to set enabled = false on one of them when I open the form - that's fine

I have two txt fields - ReceiptNo and BankPaymtId if the both have a value I want to make the button enabled = True

This is the code I have used on the BankPaymentId On Dirty event

Private Sub BankPaymentId_Dirty(Cancel As Integer)
If Me.[ReceiptNo] <> "" Then
If Me.[BankPaymtId] <> "" Then
Me.CreateOutlay.Enabled = True
End If
End If
End Sub

This is the one for ReceiptNum on Dirty event

Private Sub ReceiptNum_Dirty(Cancel As Integer)
If Me.[ReceiptNo] <> "" Then
If Me.[BankPaymtId] <> "" Then
Me.CreateOutlay.Enabled = True
End If
End If
End Sub

Nothing seems to be happening.

Even the Form on Dirty is not working now....