MAS Cross tile validation

We are using MSA - Mobile Sales, primarily for Opportunity management.

In MAS, we are trying to build cross tile validation. On one tile, we want to check if a field on another tile (all within the same BO) is entered. If not, we want to pop up a dialog box, where the user can choose a value, and then store the value in the field.

I was trying with the 'InputBox$' and can enter a value.... but I cannot get this to save in the BO. I also cannot get the list of possible values from our Combo Engine.

I would appreciate if anyone could offer some assitance on this.