Let A2:B7 house the sample you provided.

In column C from C2 on, enter the first day dates of the month/year
combinations:

1-Jan-2005
1-Feb-2005

etc.

In D2 enter & copy down:

=SUMIF($A$2:$A$7,"="&C2,$B$2:$B$7)-SUMIF($A$2:$A$7,""&EOMONTH(C2,0),$B$2:$B$7)

Turk wrote:
Dear all,

I have a worksheet as below

5/1/2005 50
23/1/2005 100
18/1/2005 120
2/2/2005 12
12/2/2005 24
4/3/2005 15

I want to sum up the total of each month to get

Jan 2005 270
Feb 2005 36
Mar 2005 15

What should be the formula?
thanks....

ims



--

[1] The SumProduct function should implicitly coerce the truth values to
their Excel numeric equivalents.
[2] The lookup functions should have an optional argument for the return
value, defaulting to #N/A in its absence.