Equation Modeling Project Question

So I am making a vba program that finds the constant values when modeling for linear, exponential, power law, and michaelis-menton form. I have gotten linear, exponential, and michaelis working but I have not gotten power law working. I have tried setting up a solver method but that is very buggy. I also thought about natural logging both the x and y values but I get errors whenever one of those is zero or negative. Can anybody think of a way around this? Or is there some way I can disregard zero and negative points and still get a calculation? I saw somewhere that there is a way to change error messages to plug 0 in by default with IFERROR command