>>IMO, oo-way is to have 3 textboxes and one combo. Combo.Interactivechange event will reset each textbox.Value and Combo.Displayvalue
>
>The problem here is that the format we want (to be identical to some rows of textboxes) has the 4th field needing the combo selector, but the key selection fields are 1 & 2. So I can't put a combo separately on 1 or 2, only on 4, or else one very long combo, as I'm trying to do. I can't change the field order, either. Something of a puzzle to solve :)

It doesn't matter what field will go to Combo.Value. As long as you handle Combo.Displayvalue (Combo.Style=0) you are allowed to put whatever you want into combo's text portion:
***Combo.Interactivechange event
This.Displayvalue="whatever"+table1.field4+"something else"
Thisform.Text1.Value=table1.field1
Thisform.Text2.Value=table1.field2
Thisform.Text3.Value=table1.field3