Your target can be put in as an option on /cast macros, not a huge deal on 2-liners like you got, but if you're nearing 250 chars it's nice.

And you get to attack something you aren't targetting, nasty surprise in PvP.

Anyway:
[code:1]#showtooltip Lesser Heal
/cast [target=mainbox] Lesser Heal[/code:1]