Craft Contingent Spell( Complete Arcane, p. 77)
You know how to attach semipermanent spells to a creature and set them to activate under certain conditions.
Caster level 11th,
You can make contingent any spell that you know. Crafting a contingent spell takes one day for each 1,000 gp in its base price (spell level × caster level × 100 gp). To craft a contingent spell, you must spend 1/25 of this base price in XP and use up raw materials costing one-half the base price. Some spells incur extra costs in material components or XP (as noted in their descriptions), which must be paid when the contingent spell is created. See Contingent Spells, page 139, for more information.