lan to lan rule with sonicwall pro2040 enhanced

Hello,
I had a question about a lan to lan rule. I have two pc’s sitting on my internal network attached to the same cisco switch. My main sonicwall pro2040 is attached to that cisco switch as well giving everyone interent access. I would like to keep pc A from access pc B in any way. Would a lan to lan access rule do this for me, or do those two pc’s even go to the firewall when they are trying to communicate with each other on our internal network? I am guessing that lan to lan rules are for certain servers, ect.. that are connected to the additonal ‘x’ ports on the firewall? Any help would be appreciated. Thanks