Steps to create % column in Cross Tab report

[nbailey]

 I am hoping someone can help me out with how to add a % column to an aggregated field in  Report Studio Cross tab report.  The enclosed report is simple enough.   I am rolling up student ids based on academic  year.  I am trying to add a 3rd column to this report which will calculate the % difference between 2011 and 2010 enrollments.
This is a multi query (2 query) report.   One query for currYr (2011) and one Query for PriorYr (2010).  contents of the query's are as follows
dbname
id
academic year
campus code
program
amt

I really don't need the amt field... i use that to roll up the pidms... was trying to create multiple variables to store the id totals from each query.  Could just use the id as my aggregate. both work fine.

Enclosed find more report details...

I need to :
1.  find a way to capture the aggregation amount for each year 2011 and 2010.

2.  use those amounts to create a percentage column in my report .


Thanks for any help you can give me on this .