Is it not possible to make edits to a field that is attached as the controlsource of a Dropdown combobox?

For example, if I have a character field, FLD, in table A and I put a combobox on a form. I then set the Style to 0-Dropdown Combo, RowSourceType to 3-SQL Statement, RowSource to "SELECT A.FLD FROM A INTO CURSOR C_TMP" and the ControlSource to A.FLD.

In the Valid of the combobox I put:

REPLACE A.FLD WITH THIS.DISPLAYVALUE
THIS.REQUERY()
THIS.REFRESH()

When the form is run, I can edit the value shown in the combobox but it never shows in the dropdown list or in the text portion. Anyone have any suggestions to make this work?

TIA