Need help with formula for expense sharing

I was trying to create a formula for expense sharing between three friends. Though it looked to be simple at first, it does not appear to be.

Overall requirement: When three people contribute different amounts for an expense item than their actual share, how can we come up with a formula which shows what amounts need to be exchanged between them for a reconciliation? Attaching the excel sheet. I was looking to fill out the cells in yellow with formulae.


Ganesh