Hi, tintincute.

Could You please specify your problem(I'm not sure what is your problem)?

But if I inderstand You:

The KV Diagram is used to obtain minimal DNF. So, first of all, obtain values for your expression(S= !A * C * !D * !B + !A * C * D * B ), then use your diagram to obtain minimal DNF(if you understand Russian I can give a link to algorithm )

So, if You will specify your problem I'll try to help You.