The Craft contingent spell feat description says
Craft Contingent Spell Type: Item Creation
Sources: Complete Arcane Unapproachable East
You know how to attach semipermanent spells to a creature and set them to activate under certain conditions. Prerequisite: Caster level 11th. Benefit: 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 x caster level x 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.
The DMG, at page 215, says
Prerequisites: Certain requirements must be met in order for a character to create a magic item. These include feats, spells, and miscellaneous requirements such as level alignment, and race or kind. The prerequisites for creation of an item are given immediately following the item's caster level. A spell prerequisite may be provided by a character who has prepared the spell (or who knows the spell in the case of a sorcerer or bard), or through the use of a spell completion or spell trigger magic item or a spell-like ability that produces, the desired spell effect. For each day that passes in the creation process, the creator must expend one spell completion item (such as a scroll) or one charge from a spell trigger, item (such as a wand), if either of those objects is used to supply a prerequisite. It is possible for more than one character to cooperate in, the creation of an item, with each participant providing one or more of the prerequisites. In some cases, cooperation may even be necessary, such as if one character knows some of the spells necessary to create an item and another character, knows the rest. If two or more characters cooperate to create an Item, they must agree among themselves who will be considered the creator for the purpose of determinations where the creator's level must be known. (It's generally sensible, although not mandatory, for the highest-level character involved to bet considered the creator.) The character designated as the creator, pays the XP required to make the item. Typically, a list of prerequisites includes one feat and one or more spells (or some other requirement in addition to the feat). When two spells at the end of a list are separated by "or", one of those spells is required in addition to every other spell mentioned prior to the last two. For example, the prerequisites for a ring of three wishes are "Forge Ring. wish or miracle", meaning that either wish or miracle is required as well as the Forge Ring feat
Can two characters collaborate to create a contingent spell with this feat?
Will the contingent spell depend on the will of the character who puts the spell?
More specifically, I have a cleric and I want to buy a contingence with Antimagic Field. The condition is: if an enemy casts Mage’s Disjunction, the contingency is activated. However I also want to be able to interrupt the Antimagic Field. I thought that if my cleric casts the spell, he can also interrupt it later as he is the main spellcaster.