I finally got my cbo to display the group # when selected (not sure how, but it now works).
The main form has three fields: cbo, and two other fields. There are several subform also. Each form and subform have their own tab indexes. The group # on the main table is the link for all subforms.
Problem: after I select the group, it displays properly in the subforms, but when I hit tab, it advances the record instead of going to the next tab index.