macro help....if its possibleFollow

Trying to make a macro, not sure if its even possible but....
My attack bar is shift 1, and my healing bar is shift 2, I tab target nearest enemy, and q/e cycle closest friendly targets
what im trying to do is have shift 1 bar pop up when I tab target nearest enemy (I almost never mouse click a target friend or foe), ie im running around in ab keeping myself and friends alive, an enemy approaches I tab target him and my action bar automatically switches from my healing bar to my attack bar, seamless kinda like the bar change when you enter shadow form, or stealth, or stance changes

and in the same breathe, have one the will change me back to healing bar when I q/e a friendly target or when I use one of my self target macros

all this will do is save me the time of hitting shift 1 when I target something, then hitting shift 2 when I go back to healing

very limited macro experience, I have a few copy pasted macros from here, and a bunch of self target/focus target macros, and inner focus attached to almost everything

there is prob an addon that will do this, but I try to keep my addon memory usage to a minimum (I turn everything off in a bg), 10 yr old pc = I need every byte of ram I can get.

I don't know how to change bars with a macro. But you can use the same bar and have the button do something different depending on whether the target is an enemy or friend, for example:

#showtooltip
/cast [harm, nodead] Shadow Word: Pain; [help, nodead] Renew;

That'll cast SW:P on an enemy target or Renew on a friendly target. No need for multiple bars, it'll show the tooltip for whichever spell applies given the conditions, so the button will show up correctly based on your target.