Accessing data in a child table

I have set up a Parent/Child table relationship using the UD100/UD100A tables. I have successfully added two ultra combo boxes to my SO entry form with one populating with data from the parent table (UD100) and the other populating "BeforeDropDown" with data from the child table (UD100A) related to the selected value in the parent combo box.

I now need to populate textboxes with data from the child table (UD100A) based on the selected value in the child combo box. I have no problem getting the key value from the combo box, but I do not know the method to use to gain access to the child table (UD100A). There is not an adapter to use to connect to the table.

Do I have to somehow access the table using the adapter for the parent table?