The site where the spreadsheet is blocked for me. You could try OpenOffice. It's a free Office alternative.
Anyways, I believe that I read that a good serving size was about 1/4 - 1/3 pound of meat.
Assuming 1/4 pound, you'll need 250lbs of cooked pork/brisket.
Assuming 1/3 pound, you'll need 334lbs of cooked pork/brisket.
IIRC, pork butts lose about 50% of their weight, so you'd need 500lbs of pork for 1/4lb servings and 668lbs for 1/3lb servings.
Brisket the math gets a little harder. IIRC, Briskets lose about 40% of their weight, so you need 416lbs for 1/4lb servings and 556lbs for 1/3lbs servings.
My math may be off, so double check it.
Large Big Green Egg
22" Weber Smokey Mountain Cooker
Brinkmann Smoke N Pit