Running Cumulative Sum on every Nth column

[mollys]

Currently I have a spreadsheet with four columns. In the worksheet I may replicate these columns up to twelve times:

In "Biller Next Steps" for January, it references C2 (Invoiced Amount January).
In "Biller Next Steps" for February, I need it to sum C2 and G2.
The only way I can figure to do it now is to change the formula in that column depending on how many I have.
Is there a way to write the formula so that it will continually add the Invoiced Amounts?

Please let me know if you need more info!!

THANK YOU!

 

[AlphaFrog]

Put this in D2
=SUMIF($C$1:C$1, "Invoiced Amount*", $C2:C2)

It should replicate for the other months and give you a running total.

 

[mollys]

This works PERFECTLY! Thanks so much