Selecting elementst by level

I have creted this in Dynamo.I want this to work so that I can select which level I will work with and then replace the value of all elements in this level. The parameter I would like to change is “magi_ov2”. I get an error in the end, is this because the parameter magi_ov2 not exist on all element?

Is there also a possibility to be able to select elements by system or all MEP elements.

Hi @kjetil.johansen

Which MEP category elements your trying to select?

What does the error says?

What I really want to do is to select one level and then select one system or every system in this level model, change the value of the parameter magi_ov2 to another value.

Try that?

Which system your talking here? MEP?

Yes the system have a specific name. This name can change between projects.