Preventing a divide by zero error

This sounds like an easy an easy thing to check for, but here's what is going on:

I'm studying (on my own) RPG IV using Stanley Myers' book, "RPG IV Programming on the AS/400". I'm doing the programming assignments at the end of Chapter 5, and assignment 5-2 wants "Include the control that prevents a divide-by-zero error". As far as I can tell, this hasn't been discussed in the book yet; so I don't want to jump ahead with a solution that isn't what they are really looking for.

This is what the line in question could be something like:

C EVAL GRPFT = NETPRICE / GROSSPRFT

Is there some EVAL option I'm missing for this? Setting indicators is discussed, but for the life of me I don't see anything related to divide by zero.

I did some searching, but I found what I would logically do to check for a zero in the variable before doing the math. That hasn't been covered in this book yet, so I'm guessing there is something else to it.

Thanks,
Clay Carley
Sonic.net/ Sonic Telecom