Excel stores dates as serial numbers. The date 1/1/2009 has value 39814.
So if each of your money values are below that value, you could use
=SUMIF(A:A,"<39814")
Alternatively you could use a helper column. In B1 (or some other column far
to the right, and maybe hidden) enter =CELL("format",A1), copy down the
column. Cells with dates will have formats of Dn (where n is a digit) while
cells formatted to show 2 decimal places will have F2, while those with
currency format will have C2. Very odd: a long date such as 1 January 2010
seems to have format G (general) - I am using Excel 2010 beta
To sum currency formatted cell: =SUMIF(B1:B100,"C2",A1:A100)
Note: the CELL function is not volatile so if you reformat a cell the
formula will not update until the worksheet is next recalculated. You can
force this with F9.
If the helper column is not acceptable, maybe someone with give you a VBA
solution.
best wishes