managing #overflow when concatenate

In my current situation, I have an existing report that shows #MULTIVALUE in four different fields. I concatenated each field using variables like VAR CONCAT/ VAR MAX CONCAT etc. using the procedure described here:

bi.scribe: Converting rows into a single cell (comma separated list) in WebI

I have done this in many reports which all contains a big quantity of data. Therefore it works fine for maybe 15 pages until it stops and gives the #OVERFLOW error.

Is there a way to get around this problem by altering the variables? Or is there some other better way altogether to do this?

Really thankful for your help!

//A