Global DataStore and Combo boxes

I have a grid that contains a couple RO fields. The user is able to click on these grid rows and edits the details in the adjacent form. The form/grid/datastore sync up just fine initially.

Two of the fields on the grid correspond with combo boxes on the edit form. When a row is selected the form seems to populate correctly but calling “save()” does nothing - I don’t get any errors in firebug and the grid/datastore don’t update with any of the changes.

Ideally I’d like to save the ID of the combo box to the database but display the description to the user. Additionally, (the two combos being “Location” and “Code”) the “Code” combo should be limited based off of the selection in “Location”. I’m sure that part can be easily done - I’m more concerned about the saving and displaying the combo information correctly.

Would you please share the detail description regarding this or link that describe it well. If you have pictures please share them here.