I am currently working on an excel forecast sheet that automatically replenishes inventory once it is, or goes below zero (safety stock not accounted for). I have tremendous difficulty with this school assignment so any help is greatly appreciated.
Well, since it's a school assignment, I'm sure you don't actually want somebody to, you know, DO it for you. You don't give any indication of what you've even tried so it's a bit difficult to know what suggestions to make.
For starters, though, check out the IF and IFS functions. Here's a good website for your research.