Stop data entry on subform if control on form is Null

[cariengon]

I am trying to not allow a user to enter any data into a subform on a form, if a control on the form is null. I've set the focus to be on the control when the form is loaded and then I'm assuming that if I do a Lost Focus event when the user somewhere on the subform, I'll get the message that I want.

What am I missing here? My code is the following:

Private Sub cbo_MonthYearSelect_LostFocus()
If Me.cbo_MonthYearSelect = Null Then
MsgBox "You must select a Month period.", vbOKOnly
Me.cbo_MonthYearSelect.SetFocus
End If
End Sub

Should I be trying to set the code on the gotfocus of the subform? I tried that and that doesn't seem to work either...

Any ideas?

Many, Many thanks in advance...
Carie

 

[cariengon]

Okay - Step 2:

I just got this to work, by using IsNUll(cbo_...)

BUT, since I clicked on the subform it's not returning my focus to the control on the main form. I even tried using the
Forms![101_Issue_TimeEntry_frm]![cbo_MonthYearSelect].SetFocus
to ensure that the focus will go back to the main form.

Should I be using a version of this code on the load event of the subform - or the gotfocus event of the subform? I can't control what control the user will click on, so I don't want to tie it to a field. When I have tried it on the current or sfrm load, it doesn't seem to take the code...

UGGGGHHH!!

 

[RichUK]

Private Sub Collections_subform_Enter()
If IsNull(Me.CustomerID) Then
Beep
MsgBox "There are no Customer details entered yet, please correct this"
txtSurname.SetFocus
End If
End Sub