The full path would be
Forms!frmNameOfMainForm!ctlNameOfSubformControl.Form!ctlNameOfControl
If the code is on the main form then Forms!frmNameOfMainForm can be replaced
with Me. The subform control is a control on the main form that acts as a
container for the subform. To get the name of this control, open the main
form in desgin mode, open the Properties sheet, click on the subform ONE
time. The Properties sheet should show the name of the subform control. If
you click a second time, you'll be in the subform and the Properties sheet
will show the name of the subform, not the control holding it.
Controls on a tab are refered to as if they were on the form itself.