Rewrite a functioning VBA-tool

I have an already functioning VBA-code, which hast to be modified to fit an other case. A new variable hast to be added, which also affects already existing variables. The VBA-skills you need do not have to be very advanced, but you need enough experience in programming because understanding the problem is pretty hard. You also would have to work with a program called open solver. But when you look at the open solver-part in the existing, functioning tool you should quickly understand how it works. The VBA-programm consists of 3 optimization steps. I already changed the first step so it fits my case (and it works). Step 2 and 3 still have to be changed. I guess it takes half a day for understanding the tool and one day for each optimization step, so 2,5 days in total. The problem is that I need the solution in one week and not later. So please consider if you have enough time!