number of households within a radius

I am writing a business plan and need to figure out my potential customer base. I need to figure out how many households are in a given size radius. I have been able to dram the radius maps, but don't know how to figure the actual or aproximate numbers in that radius given the census tract information. Is this application even possible? Do I have to make an educated guess (calculus and geometry were a real loooooong time ago :? ). Thanks for any help you can provide :)

First, map the data to the map. This is done by,

Date->Data Mapping Wizard->Shaded Area->US Demo Data

Select Data Field or Column (Households (2002))
Divide by (none)
Show Data By (Census Tract)

Formatting: use Discrete Equal Ranges, use all 8 possible ranges

Once this is done, draw a radius (use the Radius tool from the Drawing toolbar) using your location as the center. MAKE SURE THIS RADIUS STAYS SELECTED.

Next, choose Data->Export to Excel. This exports all of the Census Tracts whose centroid is within the radius circle ALONG WITH the households for each census tract into Excel. From there it's easy enough, of course to add them up.