Replace the print with SendChatMessage:
Lua Code:
/run if UnitExists("target") then local h,m = UnitHealth("target"),UnitHealthMax("target") SendChatMessage(format("%s's Health: %3.1f%%", UnitName("target"),(h/m)*100), "SAY") else print("No Target") end
See the docs for restrictions on using
SendChatMessage.