iRule to filter based on subnet

Greetings all, I have been reading some other forum posts about using iRules to filter client IP's, and I have come across some discussions about how to get subnets to work, but I am still a little lost. I was hoping that someone could point me in the right direction.

We have many remote companies that need access into a billing portal that we run. I have built a pretty straight forward iRule that does this:

when CLIENT_ACCEPTED {
  switch [IP::client_addr] {
    173.160.151.225 {
    }
    [several dozen more ip cases trimmed for readability]
    default {
      drop;
    }
  }
}

(sorry for the formatting, the forum software on this site is really goofy. Something about not being able to paste rich content?)

So this works pretty well. But, the problem I have is that some of my clients use various subnet ranges for their access. And I can't figure out how to match for my clients that have addresses that are like a /28? Simply putting the subnet and CIDR into the switch doesn't seem to work.

Currently this is running on some 1600's with 9.4.x on them. We are planning a roll out of 10.2 soon though. Hoping someone can offer me some help.