xcacls.vbs doesn't support UNCs; you'll need to map a network drive to the share/folder you want to change and then use the drive letter and path.
In a command line:
net use X: "\\she11nt\groups"
cscript /nologo xcacls.vbs "X:\users\common\test" ...
net use X: /delete
You can of course use a deep mapping as well:
net use X: "\\she11nt\groups\users\common\test"
cscript /nologo xcacls.vbs "X:\" ...
net use X: /delete