Rolling Sum with two unique variables

[rtsripchikexcel]

I am looking to build a formula and i am stumped. I have a column of unique names and my row headers are months. How do i put together a formula that does a rolling sumation by unique by month. Any ideas??

Thanks.

 

[rtsripchikexcel]

The way i was trying to do this was using the index funtion to get a lookup for name and month i just have no idea how to incorporate a rolling sum into this. Am i looking at this incorrectly? Any ideas

 

[wigi]

I do not know for sure it will work, but did you consider pivot tables already? They're quite powerful and often take away the need for writing difficult formulas.