The short answer is: NO. But what I can do is give you some guidelines to how you could improve your mix in order to make it suitable for mastering.
Say you submitted a mix where 2 guitars compete in certain frequencies. I'd tell you to seperate them by boosting guitar 1 in fx 1.5 Khz and cut the other at the same frequency a few dBs. The same goes with guitar 2 now at 2 Khz. Now I've gained more control as they are not competing anymore, thus giving me the chance to work on each in their own frequency domain.