Requested WoW macro

Hi, I was wondering if it was possible to have a macro that would cast if I was targeting an enemy or a friendly player and cast [Spell 2] if I was targeting myself.

I hope thats specific enough.
The scenario I want for this macro is for when I kill a target yielding experience/honor, I get the Crusader talent which increases the heal of Holy Light by 300%, which makes Holy Light well worth the cast time, but unless I have that active I just want to cast flash of light which is more effective for pvp situations.
So say I’m targeting an enemy, I click the macro and it casts Flash of Light on myself (because I have auto-self cast checked on interface), or if I’m targeting a friendly it will cast flash of light on said friendly. But if I’m targeting myself, it will cast Holy Light.