I have a phone plan that gives me 120 minutes for a month.

100 minutes can only be used after 7pm, and 20 can be used whenever.

I have an entry into how many offpeak minutes (b4) and how many peak minutes(b5) I think I will use in a month.

so what I want to say is if I use 20 offpeak minutes (I am given 20 free) for it not to read as a zero.

If I use anything up to 120 offpeak minutes, the end should still read zero, but if I use 21 peak minutes, the result should read 1.

Or another scenario would be 19 peak minutes, and 101 offpeak minutes to also read zero (max limit)

Im thinking it would be a complex =if function, but not really 100% sure, as I have been playng around with this for a while.

What I have worked out so far is that I should be using an if function (maybe I am wrong) ..

Im not sure if I have conveyed my problem too well so if you need any further explanation, please ask :P

Assistance would be appreciated, because Im trying to work out a calculator for me and my friends to find out what plan I would be saving the most money on ...

Cheers.