Woody,
Alternatively, here's something to try:
1. Copy your current calculation to the clipboard.
2. Drop an unbound field underneath your table frame (or wherever it makes sense).
3. Right-click it, choose Define Field, click the calculated check box, and then past in the calculation.
4. To the left of the calculation, type "sum(" and to the right, add "

" (no quotes, please).
5. Choose OK and then try it out.
Many common calculations can be summarized this way. However, there are a fiew that can't. Instead of going into a lengthy discussion of that, try this and see if it works. If it doesn't, then post your calculation and we'll go from there.
The short answer is that there are times when it's necessary (or desireable) to save calculated field values to a table. Once you've done that, it's easy to summarize them using other calculations.
(FWIW, I'm about half-finished with an article for the site that describes this. Let me know if you need it more quickly.)
Hope this helps...
-- Lance