StrikerDubstep

Hey everyone, i just wanted to ask something. Can u add like a file where u can change the errors while joining a server? Like if i want to join a server and im missing a mod there is the notification something with:You are missing forge or something. Or please install Mod [NAME HERE] bla bla bla.. Is there a way where u can change those messages? And if not can u add one or tell me how to add one? BTW: I used the Search function but found nothing related to my Problem/Question! Much appreciate!