Running Sums for percentages in BO XI 3.1

[burdej]

Hi

I have a formula to calculate percentages of completed applications
per month :

=(Count([Compltdt]) )/(Count([Appln Id]) In ([Policy Input Date])*100

This is shown horizontally on a cross tab. They actually want culmulative percentages per month so if it was:
COMPLETED
Jan Feb March Apr
INPUT
Jan 25% 10% 15% 10%
Feb 15% 10% 12% 5%

What I need is:

Jan Feb March Apr
INPUT
Jan 25% 35% 50% 60%
Feb 15% 25% 37% 42%

I have tried using runningsum to be reset at the input date
The forumula I have written is:
=RunningSum(Percentage(Count([Compltdt]) )/(Count([Appln Id]) In ([Policy Input Date]);[Policy Input Date))*100

Any suggestions gratefully received!