How to prevent file owner from changing/deleting their own file? Linux CentOS

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http://serverfault.com – This is NOT your standard "how do permissions work" question! I'm thinking the answer will probably involve ACL, but I don't know how exactly. I've messed around with standard permissions, guid, sticky bit, etc. Doesn't work. What I want: User will upload files. User will have ability to change permissions on files to allow execution. But user will not be able to change the contents of file once it's created. And user will not be able to delete the file. Please help! I've been tearing my hair out for hours! (HowTos)