Ok, before I address this, I would make a suggestion regarding your PingPC function.
At the moment, there's no point in it being a Function because you don't return a value. I would change it to this
Then, you can just do the following in your Loop
Now, as for your exclusion list I would use a Dictionary object instead of an Array. And use the Exists method to check whether or not the PC you want to check is in the Dictionary
You would do that check after this line
Go and read up on Dictionaries and have a bash at it. If you still need help, come back here