Quintessential Wizard 4E metamagic feat: Contingent Spell

[Isomenes]

Greetings,

Regarding the feat Contingent Spell in the Quintessential Wizard, is the spell expended when casting the contingency, or is it expended when the contingency is triggered?

Can the wizard cast other spells between the time the contingency is set and the time it is triggered?

Thanks!