I am hoping my explanation of this is clear enough...
Say I have an iframe in one page using src "http://potternet.duoservers.com/%3Faction=f_order&plan_id=48174&css_file=htt://www.potternet.net/css/form.css&otype=", how would I use links from other pages of my site to change the "plan_id=" part to show a different number in each case?

I figure that my links from other pages can be to "set-up-hosting.html?[relevant id number]" in each case.

the question is, can I replace "plan_id=48174" with something like "plan_id=$plan" and use jquery to write the relevant number from the querystring of a link from another page of my site?