Looking for PRODUCTIF() workaround

[baseballprof]

I am having a hard time coming up with a good workaround for a PRODUCTIF() function. Here's the issue I'm trying to solve.

I have over 1,000 rows of data with dates in Column A and values in Column O. I would like to multiply all of the values in Column O with the same date in Column A, and have this value return in Column P. Visually, it would look like this (ellipses used to space columns properly):

Col-A .. Col-0 .. Col-P
4/1/13 .. 2 ....... 40
4/1/13 .. 4 ....... 40
4/1/13 .. 5 ....... 40
4/2/13 .. 3 ........ 9
4/2/13 .. 3 ........ 9
4/2/13 .. 1 ........ 9

I have attempted to do this using the following array but to no avail, this one for the output in P1: {=PRODUCT(IF(A:A=A1,O:O,1))}

I would be open to a solution using Macros, but I am not very good with Macros (perhaps this is a good time to learn). Really any solution would be very welcome. Thanks in advance!

 

[AlphaFrog]

Try something like this.

=PRODUCT(IF($A$1:$A$1000=A2,$O$1:$O$1000))

This is an array formula.
Confirm with Ctrl+Shift+Enter
It references a fixed range instead of the entire column.

 

[baseballprof]

That was the solution! Thanks a lot. Good to know I wasn't too far off!