Sum with multiple conditions

[John]

I'm trying to write a sumproduct formula with mulitple conditions:
C6=4/25/08
C44=Project121

I'm using:

=SUMPRODUCT(--(Sheet1!K$2:K$50001<=--C$6),--(Sheet1!E$2:E$50001=C44),Sheet1!T$2:T$50001)

I want to sum the values in column T with the specific data in C44 athat has
a date less than 4/25/08. The data in column C changes, so C43 could be
Project151. Also I want the date to alway be the current date, that is why
I'm refrencing it to a specific cell, using =today(). I keep getting a #ref!
error.

The previous formula I was using was working but it didn't factor in the date.

=SUMIF(Sheet1!$E$2:$E$50001,C44,Sheet1!T$2:T$50001)

Can anyone help? Using Excel2003

 

[T. Valko]

=SUMPRODUCT(--(Sheet1!K$2:K$50001<=--C$6),--(Sheet1!E$2:E$50001=C44),Sheet1!T$2:T$50001)

If C6 is a true Excel date then you don't need the double unary: --C$6. If
C6 is a TEXT string that looks like a date then the double unary will coerce
the string to a true Excel date. Other than that, there's nothing wrong with
the formula. If Sheet1 doesn't exist then you'll get a #REF! error. Or, do
you have #REF! errors already in any of the ranges?