Changing System messages.

Hi, experts,

     I want to change system messages.

     I can change only two messages,"Your entry has been saved.Saved failed."

     But I can't change AlternativeKey error messages.

     When I enter the same alternative key, it shows its system message that is not quite helpful for the user.

     I want to replace that kind of message with my custom message.

     Please confirm if it is possible.

Regards,

May T.