Requested WoW macro

I want to announce to any channel I want, preferably general channel, that a rare has so much % life left. Since anyone can get loot it would be nice to announce to other players near by. I tried working on it myself and I came close. But, with the macro I made it only says my macro in say, I haven't figured out how to change it to say in general chat.
Here is what I got;
/run local t="target"SendChatMessage("Rare "..UnitName(t).." has "..(UnitHealth(t)/UnitHealthMax(t)*100).."% health left!")

If you could get this one to work or make one yourself that would be awsome.

Thanks for your time.

~Zmeu