catzmeow - I don't fully understand your issue, however, I will give you some general tips that may come in useful:
-To get around the 7 nested IFs constraint you can have the 7th IF statement refer to another cell in excel which contains another nested IF argument.

-Have you considered the vlookup formula to find the commision to apply? You could concatenate the results of "Line" "Type" and any other criteria to create a 'code' that would be looked up in an array. (to concatenate use the ampersand '&' between values). Then an array with a column containing every unique code (i.e., RedRed1, PurplePurple2, etc) and the adjacent column with the commison rate. Then vlookup against that array.