One thing you could do is dynamically create the file that you're going to call to include all of the variables in it. You can do it using Javascript. Below is an example that I used to link to Expedia.com's driving directions site. If you'd like the full page, let me know and I can post it, but here's the Javascript portion of it.
<SCRIPT LANGUAGE="Javascript">
<!--
function submitme()
{
var astr=document.findus.street.value.split(" "

;
var str=astr.join("+"

;
var acity=document.findus.city.value.split(" "

;
var cty=acity.join("+"

;
var myactionurl = "
+ str + "&city1=" + cty + "&stnm1=" + document.findus.state.value + "&zipc1=" + document.findus.zip.value + "&cnty1=4&strt2=3264+Williams+Rd&city2=Columbus&stnm2=Ohio&zipc2=43207&cnty2=4";
document.findus.action = myactionurl;
document.findus.method = "post";
document.findus.target = "new";
document.findus.submit();
return true;
}
Let me know if you'd like some help plugging this into your form.