Custom Adaptor for UD table

I have a UD table listing codes i need to apply to Suppliers. I have an UltraCombo on the supplier, and I ham using UD03Adapter.

In UD03, I have a checkbox intended to limit the choices for this Combo Box.

Is it possable to create a custom Adapter that can limit this list for me? e.g., can i put a "where" clause in somewhere, like: WHERE UD03.Checkbox01 = TRUE.

Any suggestions on how to accomplish this would be great!!

Thanks,
Keith Walter