Hello, you can activate or desactivate with TriggerIf.
For example :
<PlugIn Id="_ImposeDisplacement" .... TriggerIf="it < 20000 and it%100 == 0" />
will trigger your plugin each 100 iterations if the iteration number is lower than 2000.
<PlugIn Id="_ImposeDisplacement" .... TriggerIf="not(it < 20000 and it%100 == 0)" />
will untrigger your plugin each 100 iterations if the iteration number is lower than 2000.
That's the same thing, you just have to put not(...)
Kind regards, Damien.