Memory issues - Cumulative count?

Hi - I posted a question here a few days ago and it was answered by a kind person. The question was in regard to a cumulative count. http://www.excelforum.com/excel-gene...ive-count.html was the question and the answers I was given - the last of which I have used to good effect. Unfortunately, in my actual workbook, I have a lot of data and when I use the formula that I was given in my previous post, it says that I cannot complete the task with available resources and jams. I'm using a laptop with 8Gb memory and I was wondering if there might be any way to change the formula to make it more amenable to being used over 550000 rows. Thank you and sorry if this sounds confusing.

Many Thanks

And yes, sorry - as the last poster on the other thread mentioned, I did manually put in the numbers wrong - here is what it is meant to be (attached)