I may have mis-read what you want, but why not use the Form's On current event to tie the combobox to any changes in the bound field on the form. Example, if Combo01 is used to select an unbound record (in an AfterUpdate Event etc), put this in the On_Current Event for the form:
Combo01 = Me.BoundFieldTextbox
If you then scroll through the navigation buttons, the combobox automatically changes to match.