Formula to calculate votes for members

Hi All,

This is the first time i've used a math forum, but i've been really interested by the posts on here. My reason for coming here is to see if I can find some help to calculate a formula. here goes..

This organisation called RTSP has lots of members who are allocated votes according to how much they pay. However so that they always have a quorum, the number of votes changes depending on how many people vote.

I need a formula to be able to work out for x number of votes on the day, how many should each organisation have based on their absolute allocation.

I hope this makes sense, if anyone can knows the solution, or can point me to an article to help me figure this out, I would really appreciate it.

thanks Simon,