Search for any "Disarm Bomb" spells.
Search for any "Hinge Breaking" spells.
Search for any "Destroy Enchanted Doors that are mean to you" spells.
Search for any "Dig a hole out a building that has Sux Magic Books and a bomb in it" spells.
If you don't find anything, sit in a "thinking man" positon until something useful pops into your head.