Revoke function for public

Here is what I've tried to do for revoking/granting execution on a function: revoke execute on function encmain (char) from public;580: Cannot revoke permission. 111: ISAM error: no record found. The next two statements worked when entered individually. revoke execute on function encmain (char) from "smithte"; grant execute on function encmain (char) to "mhdwmdl" as "informix"; I am simply trying to do the following: -revoke access to the function 'encmain' for all users -then, grant access to the function 'encmain' for a list of specific users Also, how can I see the permissions for the function? Thank you, Tony