The problem with what you are doing is, you are creating a mess and don't realize it.

what you are asking for is something like...

if @wksta="Workstation1" or @wksta="Workstation2" or @wksta="Workstation3"

...but when you start sticking Not in front of those with OR... the results are going to be something other than what you are expecting, not to mention hard to follow.