/stopcasting limitations

[Aelorean]

I'm interested in having my macro only "/stopcasting" if certain conditions are either met or not met. For example, this is a useful macro for a mage (in certain, specific situations):

#showtooltip Pyroblast
/stopcasting
/cast Pyroblast

However, it'd be infinitely more useful if it "stopcasting only if casting anything other than Pyroblast". In other words, if Pyroblast is currently casting, don't do anything.

Anyway, I just wanted to make sure that this wasn't possible already before I write an addon to create a version of /stopcasting that has more bells and whistles.

Thanks!