Healing surge macro

[mistrose]

Hey guys

Fairly new to Multi boxing. Atm level 31 on a 3 team of Ele shamans.
Now I have a question if I may politely ask <3. I use a healing surge macro obviously, but I can not get it to cast on each of the 3 toons themselfs at the same time.
The only thing I can do currently is select a target and then ALL 3 have them cast on that target, but I also want it to be able to cast each 3 at themselfs at the same time.

I use this macro for follow/assist:

/target Shamishone
/focus
/follow

and

/cast [target=focustarget] [] Healing Surge

currently for healing surge.

Is there a way I can get a modifier in there? That if I dont press the modifier it casts on my focus's target. But if I press the modifier everyone casts on themselfs?

Thank you !

Mistrose