Text box won't accept format

[JimS]

I created a text box (tbPODollarValue) on an existing form. Its control
source is "=cbPONbr.column(3)" where cbPONbr is a control on the same form
sitting rightnext to my new text box (tbPODollarValue). I've set the format
on tbPODOllarValue to "Currency", and its Decimal Places to 2.

cbPONbr gets the right values. Its query is:
SELECT tblPO.ID, tblPO.PONbr, tblPO.ProjectID, tblPO.PODollarAmt,
ismember([GroupCode],moduleid()) AS Expr1
FROM tblPO
WHERE (((ismember([GroupCode],moduleid()))<>0))
ORDER BY tblPO.PONbr DESC;

tbPODollarValue displays the right value, but doesn't format it correctly.
It's formatted "general" instead of "currency".

Why?