xsl:param -- passing multiple values

Hello,
 I was wondering if someone could help me out with a problem I have run into. I have a form where I want a list of products  listed that is generated from an xml file where I pass the element position to a checkbox value, the user can then check a box of 2-4 products, click submit and I then want to pass the element positions as a xsl:parm to the the stylesheet, so it will only show the 2-4 products the user has selected. So I guess what I am looking for is something like in SQL where you would write Select all where id IN(1,4,6) etc....
 
I have checked the archives and did not see anything, any assistance would be greatly appreciated. 
 
Thank You
 
 
- Ken