1 Button press macro for actions with no GCD, is it possible or not?

[Colez 0]

I cant find a definitive answer on this, basically if i wanted to cast 2 things in a single button press in vanilla.  Say for example i had presence of mind Pyroblast macro.  If i do a macro like:

/cast Presence of mind

/cast Pyroblast

i need 2 presses to make it happen, but pom doesn't trigger GCD so should it not be possible in 1 press?  some people i've asked say its not possible, others say it is, i found an old ownedcore post from 2006 which had tons of macros specifically for 1 press, by using a /scrip spellstopcasting() in between, meaning it was possible at one point in retail WoW, but on private servers those macros dont work.

can anyone help, thanks.