[AccessD] Goto First Record subform

Hello to the list,

I have a form with a subform on it.
The subform is synced with main form via the subform's record source and a
combo on the main form.

Everything works great, except that if I am on record number 4 on the
subform and select a different value with the combo on the main form, the
subform is blank unless there is at least 4 records.
I want the subform to go to the first record each time I change the combo.

I have tried to use different variations of :

DoCmd.GoToRecord acDataForm, strFormName, acFirst

Using a public function in the sub form doesn't seem to work.

Using the afterupdate event in the combo on the main form, it tells me that
the form is not open. I have tried different ways of referring to the
subform, and even setting the focus to the subform.

I know, it would be better if I used the standard linking child/parent
scheme, but as someone here the other day said, I have reasons why not...


TIA 

Bob Heygood