How do I Stalactite fall when under?

I am having trouble making a stalactite fall when under. It sounds easy but I am having trouble making it work. I would like to make something like the example below. When crossing the X of said object set its active state to move in +Y. But I also don't want all of the stalactites to move and I also don't want other stalactites that could possibly be on a platform below fall if their X is the same. Do I need something more complex? I thought about making a invisible volume box that spans from the ceiling and finds where the ground is. I am unsure how this would be done though. Could someone point me in the right direction? thank you.

Here is a snippet of what I came up with to solve the problem. I made a volume that creates a stalactite and fills a variable with the same UID of the volume. When the player collides with the volume I make a check to see what the UID of stalactite matches and I set it to fall. I don't know if this is the right way to do this but it works.

There are a few ways of doing this. Here's an idea for you:

https://www.dropbox.com/s/sp7kkvbns4n9s ... .capx?dl=0

However, if you're using an invisible sprite and UID method, and that works, you may want to keep it. That will give you a lot of leeway in how you design your levels.

Thanks for taking the time ultrafop. I will take a look at your example when I get home.