To solve this issue, I used
CastSpellByID(228260) with the condition of Insanity > 70 to cast Void Eruption and enter Voidform. From there I used
CastSpellByID(228260) to cast Void Bolt. When in Voidform, the spell ID for Void Bolt is the same as the spell ID for Void Eruption when you are not in Voidform. Added in buff check condition to ensure I was in Voidform to cast this, and another checking the duration of the cooldown for Voidbolt (or else it chain casts when it's on cooldown and won't go down the list).