I hope I am explaining this ok....

I have the bills that are due in the first half and the ones due in
the second half of the month listed in my sheet.

I am using the Today function in a cell.
I want the Total Due this period to show either the bills due on the
first or second half of the month depending on what half we are in.

What I mean is, in the example below, there is $371.00 Due in the
first Half and $608.60 due in the Second Half.

If today’s date were the 1st till the 14th, I would like Total Due
this period to show $371.00
If today’s date were the 15th till the end of the month, I would like
Total Due this period to show $608.60

Cash Flow as of mm/dd/yy
1st $371.00

18th $48.00
16th $55.29
17th $191.00
23rd $156.64
27th $157.67

Today's Date 10/12/2009 11:45

Total Due this Period $979.60

Account 1 $-
Account 2 $849.16
cash available $0.00
to be deposited $0.00
Total $849.16

Expect to receive this week. $0.00
Expect to Be Available $849.16

Balance -$130.44