Calculate the diff. of balance of particular account

hi

I have the following info.

1. Account: PL100; Month: April2010; Balance=10000;

2. Account: PL100; Month: may2010; Balance=12000;

if want the difference of the two months:

i.e. now the result is 2000;

12000-10000 =2000

subtracting May Balance with April Balance

So this means 2000 is the transaction occured in the month of May 2010;

What is the best approach for this?

One is script Logic:

I need to select the data for Account=PL100 & respective months and do subtract >

If i use script logic ; i need to save tat difference (For that should i create one account & Save)?

or can we do this on fly while displaying report?

Thanks

Srinath