Tabard Switch Reminder

[wtfa69]

Alright, so this will be my first Addon if I can figure out how to do it, what I'm trying to do is use the message("") function so that everytime I enter a dungeon I get a message alert telling me to switch Tabards, because when I'm questing I use my Guild Tabard for guild rep but when I'm in a dungeon I like to switch to say for example my Gilneas Tabard or some other Tabard for a faction that I'm not exalted with yet, but the idea is just message("Switch Tabards") at the beginning of a dungeon when it's done loading. But as I'm new to Lua coding I can only seem to get that message to popup at WoW startup. I've googled a bit, but still haven't found anything, eventually I hope to make an addon like this that switches the tabards automatically, maybe I will, but until then could someone help me figure out how to code this? Thanks!