Revit Parameters Empty List


I’ve created a detailed family in revit with different parameters. Is there any way in which can define that if the first input is empty it would go to the second option.

In this family I want to define the parameters that if there are no input value at “MainBar_Spacing_X / MainBar_Spacing_Y” I could rather input the value in “MainBar_X / MainBar_Y”. I know that in Dynamo there is Empty.List but there is warning that the lists are null when I include the parameter “MainBar_X / MainBar_Y”.

I attached also the family I’ve created. Thanks You! :slight_smile: ColumnDynamo

Rectangular Column Detail.rfa (292 KB)