[Relaxing]

no source? noone cares

#include <amxmodx>
#include <engine>

new message[64];
new message1[64] = "Get the message";
new new_message[] = "Overwrite using this";

public plugin_init() 
    register_message(get_user_msgid("TextMsg"), "called_msg");

public called_msg(msgid, msgdest, msgargs){
    get_msg_arg_string(2, message, charsmax(message));

    if (equal(message, message1)){
        client_print(0, print_chat, "%s", new_message);
        return PLUGIN_HANDLED;
    }

    return PLUGIN_CONTINUE;
}