DAP control visibility based on value of another control

I have a yes/no field on my data access page (DAP) to indicate if a purchase
order should go to an alternate address than is stored in my vendors table.
I also have fields for altaddress1, altaddress2, altcity, altstate, altzip,
altphone, altfax, in my purchase order table. I've placed controls on my
DAP for each of these fields. Their default visibility property value is set
to "hidden", and I'd like them to change to "visible" when the value of the
yes/no field is true. I'd also like them to be "hidden" if I go to another
record or create a new record. This is the code I used in the
"onafterupdate" event in the "AltAddressYesNo" control:

if AltAddressYesNo.value = true then
AltAddress1.setAttribute "visibility", visible
end if

I also tried to use similar code in the "onclick" event and the "onchange"
event. (I'm using Microsoft Access 2003) None of them gave me the desired
results. Please help!

Thanks!
Mona-ABE