Apparently the selection from the Combobox is being assigned to the Textbox; which is really the preferred way of doing this.
The Combobox should be Unbound, and the Control Source of the Textbox should be Bound to the Field in the underlying Table.
While you can Bind the Combobox directly to the Field in the Table, that frequently leads to problems, down the road, which is why assigning the selection to another Control is preferred. For instance, in this case, if the Combobox is Bound to the underlying Field, and if an item from the Collection Table is deleted, down the road, that Control will have no data in it, simply showing #Name?. By assigning the selection to another, Bound Control, this problem is averted, when the selections in the Combobox change.
Linq ;0)>
The problem with making anything foolproof...is that fools are so darn ingenious!
All posts/responses based on Access 2003/2007