Code:
#showtooltip Mend Pet
/castsequence reset=15 Mend Pet, ,
I had found this macro once while looking up a feed pet macro for my hunter. I use a variation on it for my Holy Paladin so that she doesn't waste mana re-casting Beacon of Light (while 5 boxing, I had it bound to 5 keys). I'm at work so this might not be 100% correct but should give you the general idea.

Code:
#showtooltip Beacon of Light
/castsequence [target=focus] reset=60 Beacon of Light, ,