Shadow Bolt Proc

So I was wondering if there was a way to add into a basic castsequence macro to fire my Shadow Bolt when Nightfall procs. Here is what my current macro is.

/castsequence reset=target/combat Curse of Agony,Corruption,Siphon Life,Immolate,Life Tap,Drain Life,Drain Soul

Ive tried adding /cast shadow bolt at the end which worked but itll try to cast one after the proc is gone.