Deny Delete permission question

Anyone set the delete permission to deny and find that it still lets you delete the file? I have a testusr set up as a member of my Users group. I have given the Users group full control of a directory (which includes the right to delete subfolders and files). I have an rtf file that I want to keep testusr from deleting within this directory, but have other files that he will need to delete (temp files mostly). So I turned off inheritance on this rtf from the parent folder and denied the delete perm for testusr as well as delete subfolders and files, change perms, read perms, and take ownership. From what I understand, setting a permission to Deny will override the permissions that testusr gets from being a member of the Users group. Yet when I login as that user I am still fully able to delete that file. So just to test I also set the delete perm to deny for the entire users group and I can still delete the rtf. I've been reading through a few of my mcse books that cover the deny switch, and have been looking through forums but haven't come across one yet that has had this issue. Any help is appreciated!!!

- Josh