Excellent question, thanks!
The only thing that is missing is how to solve this type of problem - you need to split the items in the variable into their separate items, and return them as a table that can be joined or cross-applied to. Jeff Moden wrote (and several people here have contributed to) a "DelimitedSplit8K" function; a quick google search shows many posts where it's been used/referenced.
Wayne
Microsoft Certified Master: SQL Server 2008
Author - SQL Server T-SQL Recipes