this is a javascript code issue, u would probably have a checkbox which says "billing addres same as shipping"
and then on click u have to copy form fields
look up google for oncheck or onclick im not sure which for checkbox.
then in the function do a copy like so
document.form_name.billing_address1 = document.form_name.shipping_address1;
and so on
if u had posted ure code, could give u more specific code
reg
kevin