While this not my favorite way to approach this issue, it does seem to be the best suited.
I would create a delimited string of the top client ids like |1|2|5|7| (I like pipes, but any delimiter will work), and then use this to link to a subreport. (this string would be built in group headers probably, though I can see it in the detail section as well...it's up to you as to what is the easiest)
The subreport would use the delimited string to determine the top clients and what their collections are and can display them, either as 1 summary or as several broken by the clients, or however you deem fit.
It's what I would try...
HTH
Edited by lockwelle - 13 Mar 2012 at 5:08am