As Action Replay needs the (m) code to be switched on for all/any of the cheat codes to function, after it has been inputted, the code disappears from view (but is still held within the Action Replay`s memory) so itcannot be tampered with, edited, changed or switched off.
NOTE: This isn`t an issue with the very latest version of Action Replay GameCube, which offers all the codes preinstalled and does not offer facilities for inputting your own.