Distance to Level above (Duct to underslab distance)

I am looking for a way to tag a duct indicating the distance to under the floor above. Basically, I need to distinguish what is the level above, pick its thickness and I would get the offset distance to level above. Then I would substrat the element offset. Can someone help me with this? I am new to Dynamo.

Hi @jpdionne
Welcome to Dynamo forum.

Could you please show us images of your query. I am not sure may be this topic might help you Help with enchancing my code to show Bottom of duct according to offset 0 of model