You shouldn't need to link anything from your spellbook, just make sure you're spelling everything exactly as it is in the tooltip. I get annoying errors when I do it like you and kapot, so I use /castsequence instead. It requires multiple presses of the button you have the macro bound to, but just bind it to scroll up on your mouse wheel and it's nbd.
/stopcasting
/castsequence Arcane Power; Presence of Mind; Pyroblast
I have had a little bit of trouble with this method, which I think is related to the reset timer on the sequence (i.e. how long the game waits before reseting to the first action in the sequence). Not sure about the details on that though.
Edited, Oct 22nd 2007 3:38pm by AynLoD