Mortgage formula to find annual interest rate?

I would appreciate any help in finding a mortgage formula that would work. Here's the question I'm trying to solve within Excel. I lend out a mortgage of $180,932.50, compounding semi-annually, 14 year amortization and on a 4 year term. I know that the total interest paid over the 4 year term will be $33,626 calculated semi-annually, but what is the rate of interest? I'm not concerned with principle at this point. Anyone know a formula?