How to make my AI use my jump pad?

So I made a AI like this https://docs.unrealengine.com/latest/INT/Engine/AI/BehaviorTrees/QuickStart/.
I want to get the difference between “target to follow” Z vector and the AI Z vector so when it is below 50 I can set a boolean in the enemy BP that will allow (in the level BP) the AI to use a jump pad when it is overlaping, but I don’t if I

have to do it using a decorator or a service and when I do the casting what should I link to the object?