Excel 2007 : How to properly combine Sum, If, Index, and Match

Hello,

I'm trying to figure out the correct formula to do the following:

1. Match data in columns H & I to data in columns A & B
2. Once a match is found, add the values of column J and column C
3. If data exists in the A&B match, display the corresponding value in C
4. If data does not exist in the A&B match, insert H:I in the O:Q range
5. This formula will be in Column Q

I've attempted several variations of a formula, but have not been successful in getting any data to display.

I've attached a copy of the worksheet I'm attempting to perform this in. Thanks for any suggestions!