Pretty much what SharkForce said.
Planar Binding is broken for the purpose of binding creatures you or anyone else summons, because the creature must be present before you start casting, and 1h duration that started before you started a 1h casting will also finish before you finish the casting.

Otherwise, finding a "wild" creature, assistant caster or Glyph of Warning (note that the later carries some risks as the creature appears next to whoever triggered the glyph (you) and not necessarily where you want it (inside the circle), and you can't give it any commands, it's forced to attack the triggering creature) is the way to go.