3.5nd dnd – Can a caster help another to form a craft contingency spell?

In the craft quota is written

Craft Quota Spell Type: Object Creation
Sources: Complete Arcane
Inapplicable East

You know how to attach semi-permanent spells to a creature and set them
activate under certain conditions. Prerequisites: launcher level
11th. Advantage: You can create any sort that you know.
The development of a quota takes one day for every 1,000 inches.
base price (spell level x roll level x 100 in). To make a
quota, you have to spend 1/25 of this base price in XP and use
raw materials costing half of the basic price. Some spells incur
additional costs in hardware components or XP (as indicated in their
descriptions), which must be paid when the quota period is

In the DM manual, on page 215, is written

Prerequisites: Certain conditions must be met for
character to create a magic object. These include feats, spells and
various requirements such as level alignment, race or gender.
The prerequisites for the creation of an article are given immediately
following the launcher level. A prerequisite can be
provided by a character who prepared the spell (or who knows the spell
spell in the case of a wizard or a bard), or by the use of a
spell completion or spell trigger magic element or spell-like ability
which produces the desired spell effect. For each day that passes
During the creation process, the creator must use a spell to complete his spell.
element (such as a parchment) or a charge of a spell trigger, item (such as
magic wand), if one of these objects is used to provide a
prerequisite. It is possible that several characters cooperate
when creating an element, each participant providing one or
more preconditions. In some cases, cooperation may even be
necessary, for example if a character knows some of the necessary spells
to create an object and another character, know the rest. If two or
more characters cooperate to create an object, they have to agree
themselves who will be considered the creator for the purposes of
determinations where the level of the creator must be known. (His
Generally reasonable, 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 object.
Typically, a list of prerequisites includes an exploit and one or more
spells (or another requirement in addition to the exploit). When two
the spells at the end of the list are separated by "or", one of these spells
is necessary in addition to all the other spells mentioned before the
last two. For example, the prerequisites for a three wish ring
are "Ring Forge, wish or miracle", which means wish or miracle
is necessary as well as the exploit of Forge Ring

  1. Can two characters collaborate to create a contingent spell with this feat?

  2. Can the contingent spell depend on the will of the character casting the spell?

More specifically, I have a clerk and I want to buy a contingency with Antimagic Field. The condition is this: if an enemy launches the disjunction of the mage, the contingency is activated. However, I also wish to be able to interrupt the antimagic field.
I thought that if my clerk cast the spell, he could also interrupt it later since he was the main caster.