Commission calculator in Excel

Need a simple spreadsheet that calculates value of commission earned on value of sales and enables a team leader to allocate to people. Would like it to:
1. calculate the correct rate of bonus pot payable based on the value of the sales (there are three levels)
2. divide this pot up between the three types of people to be paid (introducer, presenter, support)
3. allow multiple people to be included and the amounts recalculated amongst them

Infographic of how the bonus scheme works is attached. Just need some way of automating the allocation of it.