Create a system to calculate the profit and loss for transactions

We are a trading company selling goods all over, we have multiple warehouse and many places we sell goods. We need a method of calculating profit and loss. Formula e.g Selling price - Expense = Profit The buying is done in different currency, selling in another, 3rd party cost of sales. There can be many rules and the rules need have a Date allocated, As some platforms the fees change so we need to be in a position to calculate that. We need the project done on PHP we can provide data set of the information, the script should process and give us a break down of each expense and show the profit. The person whose going to do the job should have knowledge of finance, programming logic.