Macro Conditionals via resource bar of target.

[Kunou]

Like the title suggests. I'd like to set up a macro with a conditional of resource bar (energy, rage, mana, rpower). I seem to remember in vanilla this was possible, but was not brought over with the macro system overhaul in TBC. Is it still possible for me to get this information via /script without exceeding 255 character limit? Basically I want to put Viper Sting and Scorpid Sting on a conditional based on my target's resource bar. If their resource bar is mana /cast Viper Sting, if their resource bar is energy/rage/rpower /cast Scorpid Sting. If I can't get this functionality purely through a macro, how hard would it be to jump in and write an AddOn to provide a /script function for this? I tried asking in the AddOn forum on ArenaJunkies but that didn't get me very far.