"on me" caller

[Seikosm]

So I was playing with a mage last night an every time he would cast Polymorph it would say "casting Polymorph on <insert name>." Being a healer, I was wondering if there's an addon similar to this that would shout out "on me <insert name>" so the tank knew which mob to grab off me. Anything like this? Or if it could be put into a simple macro that I'd just need to click that'd be great too. Any help you guys can throw at me would be greatly appreciated.