Multi Conditional Sum

Hi everyone. I'm looking for some help writing a formula that will sum a column if a particular product is listed in column A and a date time stamp is no more than three months old.

For example

Product1 6/1/10 6 would not be summed
Product1 9/2/10 5 would be summed.
Sum = 5

Here is what I have so far. However, it gives me a 0 and it should be 12.
=SUM((Sheet1!A2:A99="BigRewards")*(Sheet1!J2:J999>Sheet1!L2)*(Sheet1!G2:G999))

*J2-J999 is where the date time stamp is stored.
* L2 is a cell with today() minus three months or =EDATE(TODAY(),-3)
* G2:G999 are the cells I want to sum.
* I am using Excel 2007.

Thank you
`Brian