Dave, I am unsure what your requirements are looking at your attached file.
Your data model contains no fact data, this might also support my confusion.
Can you post the excel file, too, so we can see what you are trying to achieve?
In general, you can't use a table box for calculations (i.e. using expressions). You'll need to use a chart (pivot, straight table, or one of the graphic charts).
You can then look into the inter chart record functions (above(), below(), before(),top() etc.), these might help you in doing what you want (well, I honestly don't know what you want, see above).
Regards,
Stefan
