Custom VBA solver/goalseek function?

[Kelvin Stott]

Hi, I need a non-invasive custom VBA solver/goalseek function as follows:

SOLVE(Output_Cell, Target_Value, Input_Cell)

This would give the hypothetical value of the input cell that would give the target value in the output cell, but without actually changing the value in the input cell. It should just return the hypothetical input value (i.e., solution) wherever the function is used, for example in another cell.

Is this possible, and does some code exist to do this already?

Many thanks,
Kelvin