How to update a drop down with a transformation

Hi,

I had looked for a solution to this in the archives but didn't run
across it. I apologize if I missed it.

Anyway,

My situation is this.

I have a main xsl page which imports a header.xsl and footer.xsl
files. On the header.xsl page is a drop downlist that will contain the
other users that are viewing the same page. I would like to be able to
click a button on the main xsl page and run a javascript function that
I could populate the dropdownlist in the header with the update
current users of that page.

I have seen something similar using iframe where the iframe.src = the
return transformation of the servlet. But I am not sure how to
retrieve a transformation and populate the drop down..

Thanks for any help.