Horizontal Totals Of Subtotals In A Matrix

I'll admit I am fairly new to the reporting services, but I managed to figure most things out so far except this one. I have a matrix report where I have column groupings of:

Sales person
Region

Basically, the report shows sales by sales person and region, and I added subtotals to each so each salesman/region combination gets subtotals, as does each salesman entry. Now, the one piece missing is the 'total of the subtotals' so to speak. So if I have something like:

Salesman Region Sales Jan Sales Feb Sales Mar
001 A $100 $175 $50

B $100 $200 $100
C $200 $100 $50
Total $400 $475 $200
002 A $100 $175 $50

B $100 $200 $100
C $200 $100 $50
Total $400 $475 $200
Grand Total $800 $950 $400

What I want to do is sum up the totals and add another column like so:

Salesman Region Sales Jan Sales Feb Sales Mar
001 A $100 $175 $50

B $100 $200 $100
C $200 $100 $50
Total $400 $475 $200 $1075
002 A $100 $175 $50

B $100 $200 $100
C $200 $100 $50
Total $400 $475 $200 $1075
Grand Total $800 $950 $400 $2150

And that is where I am stuck. In Report Designer, with the existing matrix report as above, how do I get these horizontal totals of the subtotals?