Pass the name of the form to be requeried in the OpenArgs string when you
open frmCustomer:

   DoCmd.OpenForm "frmCustomer", , , , , acDialog, "NameOfFormToRequery"

Then use Me.OpenArgs in the frmCustomer form to do the requery:
   Forms(Me.OpenArgs).Requery

You can just use the forms Activate event.

The form then can call any other form (make those other forms model..not
acDialog). When the user closes the form, the calling forms on-activate
event will fire. So, you don't need any code in the frmGetCustomer.

Hum...the above is the reversing of your original question..is it not?

You can most certainly pick up the calling form. In fact, you would
normally use the on-open event..but you can even pick up the previous forms
name as LATE as the on-load event.

So, just declare a local module level var for frmCustomer

dim frmPrevous         as form

Now, in the on-load event, we go:

set frmPrevious = screen.ActiveForm

Now, anywhere in your forms code, you can go:

frmPrevous.Refresh           (force a disk write in the previous form)

or

frmPrevous.Requery      (force a requery in the previous form)

or

msgbox "number of records in previous form is " &
frmPrevous.RecordSetClone.RecordCount