Excel process scoring by month

Guys-

I'm looking for some help in scoring a multi-step process by month. Example:

Process Instance Number Step 1 Date Step 1 Score Step 2 Date Step 2 Score
1 3/15/2012 4 4/2/2012 3
2 4/26/2012 5 5/15/2012 4

What I'm looking for is a way to automate the scoring by month, not by step or by process instance. This process can take place many times per month and can last for months at a time. IE....I don't care what steps occurred in a month, or what processes occurred in the month....i'm only interested in the total average score for that month. In the example above, the total score for each month would be 4 (step 1 in march = 4, steps 1 and 2 in april 5+3/2 = 4, step 2 in may = 4).

I've looked at ways to pivot this and have come up empty. Any help that can be provided will be greatly appreciated. Thanks!

I just noticed that the example got messed up when I posted, so I've attached an excel spreadsheet with the example.

Thanks again!