Windows 7 how do i locally protect a folder but allow network access

[realintheory]

Hi

If the following is possible.. how do I do it ?

On PC1 I have two users A (Admin) and B (Standard User) and Folder X
On PC2 I have one user C (admin)

PC1 and PC2 are on the same LAN

I want Folder X to be accessible to A and C but not B...

????