Jim:

Good database design standards would dictate that you not store a calculated
value in the table.  This is redundant.  When you need the value, just
calculate it.

There are exceptions to this.  If youhave a variable number (exchange rate,
price paid for a stock, etc.) then you may have a valid reason to save the
figure.

If so, post back and someone can give you further direction.

In general though, this would not be the way to go.

Rick B