I think there might be a way to get those numbers right without using code. I am experimenting on the form you attached in the 4th post of this thread.
Open up the Dropdown box's properties, click the button next to Entries: and select the AcuteCare node.
For Value, click the button and select AcuteCare/DptDGA/Total
For Display, select AcuteCare/Header/Sheet
Then delete the field9 textbox from the table, and replace it with an expression box bound to field7.
This should get you the behavior you described in your initial post, but not the dropdown box behavior or autopopulating you described later. Anyway, give the above a try and let us know if it will be sufficient or if we should start digging into code.