Help for a newbie that needs to block internet access to one pc

Ok, Hi all.

Im not a computer type person.... yes i can drive them.... but this astaro has got me well confused..... (im a heavy electrician)

I need to block certain PC's from using the internet im going to keep it simple for now and say that its a permanent block not a timed one.

Now i think i need to make a group for this and then define the rules for the group. I also think i need to give the PC's in question static ip addy's which i have figured out and done because the astaro doesnt do MAC filtering... (why?)

So if anyone could point me in the right direction, that would be great!

Alternatively ill pump 400v through the astaro and throw the offending PC's out of the window....:D

im running version 8.306

Thanks