On B2 try:
=if(ISNUMBER(C2),sum(A$1:A2)-sum(B$1:B1),"")
and copy it down.
Best of luck!
--
Thanx & Best Regards,

Faraz!


"Malika" wrote:

Hello,
I am using Excel 2007. Column A records individual sales. Column C records
the date that bulk payments are made to suppliers. When a date is entered
into Column C, I would like Column B to sum the value in Column A up to the
previous bulk payment. For example, when the date is entered into C7, B7
should sum A7:A2.

A B C
1 14.40 14.40 15/03/2010
2 9.00
3 9.00
4 9.00
5 9.00
6 9.00
7 9.00 54.00 25/03/2010

Any assistance would be appreciated.