Running total of all sales in first quarter, second etc

[FMData12]

Hi,

 

I have a database containing all sales i make for different clients.

I'd like to make a running total field for all sales in the first quarter, another for the second quarter etc.

So in the end i can easily see how much i made each quarter. This field should self update upon new sales.

How can i do this?

Found a way around by doing a search for all 1st quarter fields and copying total invoice value to a container field.

Very unhandy and i have to fire a script each time a update...

Any help is appreciated very much!