Solver is a powerful analysis tool, bundled with Excel and used for optimization and simulation of business and engineering models. It can be even more powerful if used in conjunction with VBA, to automate solving of multiple models which use different input parameters and constraints.
In a simple example, there are two factors in B5 and B6. The product (=B5*B6) is calculated in B8. Solver will be used to find the maximum value of the target cell (the product in B8), subject to the constraint that both factors (B5:B6) shall not exceed a value of 4. Select Solver from the Tools menu, and enter the appropriate conditions and constraints in the Solver Parameters dialog.