Using computer names in NTFS folder permissions

I have a situation where I want to share a folder for a specific person,
but I dont want them to be able to access it from a specific computer. So
the logical assumption for me would be to add the computer name and deny
all access to that folder for that computer. However, the person is still
able to access the folder from that computer. Am I trying to go about this
the wrong way? Please advise if you can.
.