apptha market place customisation

We need someone to customize apptha market place plugin, we need to set up 4 tier of fees, depending on what tier the sellers on it would apply the fee automatically, Eg tier 1=10% fee Tier 2 = 7% fee Teir 3= 5% fee Teir 4 = 3% please only bid if you worked on this type of software, and we will only pay the bid amount,