Your formula includes the row you entered the formula in, as well as the next row. The "ending cell" in that kind of (summation) formula must be at least one row above the row the formula is entered in. So, in your case, in row 29 "=SUM(B2:B28) will work.
That did it, thanks toMACsh!
Last question, and then off to a not fun weekend
How do I make even numbers show with the decimal point?
As I said earlier, $100.00 is showing as $100.
Thanks again,
Jerry