Need Help With Rich's Error Trapping Routine

Hi guys, I was looking for a way to trap err.number 3314 (when required field is null) before Jet generates its warning. I came across an old post from Rich (below), but I couldn't make it work as yet. In the calling form, under the Form_Error event I wrote the following:

Dim f As Form
Set f = Me
Call fnValidateForm(f)

Could anyone please tell me where my error lays here? I have several forms which have several text and/or combo boxes bound to required fields and I would want to have a generic code, like the one here to trap errors before Jet shows it's Error Message.

Thanks in advance
Regards
Jaime Premy - Belém-Brasil

******************Rich's Function********************
Public Function fnValidateForm(frmA As Form) As Boolean
Dim ctl As Control
Dim Msg, Style, Title, Response, MyString
fnValidateForm = True
For Each ctl In frmA.Controls
'value in the control is required
If InStr(1, ctl.Tag, "Required") > 0 Then
' no value entered or value is null
' or zero for numeric fields
If (IsNull(ctl.Value)) Or (Len(ctl.Value) = 0) Then
ctl.SetFocus
MsgBox "You have not entered all the required fields return to the record and correct this! The record will not be saved if you do not! "
fnValidateForm = False

Exit For
End If

If InStr(1, ctl.Tag, "NumberRequired") > 0 Then
If ctl.Value = 0 Then
ctl.SetFocus
MsgBox "You have not entered all the required fields return to the record and correct this! The record will not be saved if you do not! "
fnValidateForm = False

Exit For
End If
End If
End If

Next
End Function