Ok so u want to fire a query for which the key will come from combo and later on u want to fill in info accordingly.
so Take one hidden field on ur form like this

input type=hidden name=UrKey value=< % = urKey % >

(apply proper double quotes)

In Onchange event of ur combo just write a function like
--function getOtherInfo()
--{
-- document.form1.urKey.value= document.form1.urCombo.value;
-- document.form1.submit();
--}

now onchange will submit the page and now u would be having the key thru which u can fire the query and get/assign what ever u want...

Clear...