I'd like to achieve the following:

From a view like

CREATE VIEW ShortList AS;
SELECT C1,C2 FROM A WHERE NOT EXISTS;
(SELECT C1,C2 FROM B WHERE A.C1=B.C1 AND A.C2=B.C2)

I.o.w., only items that are not already in B are can be added to B.

This produces the desired results, but, assuming that the controlsource=B and the rowsource=ShortList, the combo's displayvalue is empty.

I have tried This.DisplayValue=B.C2 and a few other things with varying results, but none that displayed the desired value in the combobox.

The second issue has to do with something similar:

Once a value from ShortList is entered into B, ShortList is requeried, and should now theoretically, be even shorter.

Not so.
It seems, that if B is buffered, this is not the case.
I don't want to force the user to click a save button every time (s)he has decided to add an item from Shorlist to B.

What to do???

TIA