Can anyone give me more information on disabling objectives in assault maps?

Here's what I want to do:

The attackers have 2 objectives they can do. One of them (A) is easy, the other one (B) is harder.
If (A) is completed the attackers will still need to complete (B).
If (B) is completed and (A) not yet, (B) will disable (A).

I'm using a ScriptedTrigger for each of the objectives. When an objective is complete, the ScriptedTrigger will execute all Movers/Sound/etc... for that objective.
In the ScriptedTrigger for the second objective (B) I immediately disable objective (A).

Objective (A) is being disabled but my problem is that it also executes the ScriptedTrigger for objective (A) instead of just disabling it. The reason is that I want different things to happen depending on which objective is completed first.

Is there a remedy for this problem or am I doing something wrong?

(Hope you understand this quite complicated explanation of my problem)

Any help is greatly appreciated.