>>When I click on the combo it looses its dislpay value. Next problem to work on. :(
>>
>>What code, if any, do you have in the combo's methods?
>I see my problem now. I have containers on a form each with its own data session. I am trying to keep in sync user container selection with form's current data session. Here is my question: Let's say a current form's session is different then the container's one in which the user selects something in the combo box. Combo's ControlSource is set to a cursor that is in container's data session. When the user changes combo's selection will combo's ControlSource be updated properly? Do I really need to change data session to get this working?

It is something wrong here. If you bind combobox to a cursor then certainly user interaction will change data in this cursor. However, to update tables you should move data (programmatically) from the cursor to table(s), and if you do it right then table(s) will get updated for any data session.
PS: also as Naomi correctly noticed that you cannot have separate datasessions for each containers.