Costing arbitrage between exchanges

I'm currently writing something to script arbitrage between two exchanges to test the concept.

I know I can determine the difference in prices by using

(ExhangeA_sell - ExchangeB_buy) <- this will give me the price difference. i.e. gross profit (before fee's)

My question, how do I take the fee's into account when calculating net profit?

Costing arbitrage between exchanges

I'm currently writing something to script arbitrage between two exchanges to test the concept.

I know I can determine the difference in prices by using

(ExhangeA_sell - ExchangeB_buy) <- this will give me the price difference. i.e. gross profit (before fee's)

My question, how do I take the fee's into account when calculating net profit?