calculating selling price

I would like to calculate selling prices in different ways, based on a choice made by the user.
Choices would be as follows:

1. Fixed Profit Amount - eg.15
2. Cost Plus eg.10%
3. To give a fixed % profit based on selling price - eg.10%

The complication is that part of the cost of the sale is variable based on the selling price - eg. a sales commission.

I've attached a worksheet.

Would really appreciate any help with this conundrum!