Hi Brian,
Here's what you need to do:
1) While in the Preview Mode, Right-click the 2011 cell header > Select Calculated Member > Select xxxx as first value > Click OK on the message prompt
2) Then, right-click the header cell for 2010 > Select Calculated Member > Select Difference of xxx and xxx
3) A new row called 'Difference' is automatically added below 2010.
4) To move this row below 2011, right-click the Header cell 'Difference' > Calculated Member > Edit Insertion formula > Comment out the existing code and use this:
Year(GridRowColumnValue("Date")) = Year(Maximum({Date}))
Replace 'Date' with the Date field used as the row in the crosstab. Make sure they are used exactly the way I have above - first part should have double quotes and the second part should have parenthesis.
-Abhilash