Hi,
I was wondering if it possible to take the first number from each list and use it as a prefix for all of the rest of the numbers? My list on the left has 317 (room number) and the rest are the door marks that are within that room. The result from the far right + is what I’m trying to achieve - combining room number and door marks for a parameter. Using List.GetItemAtIndex works to a certain extent but I have 250 rooms in this project and doing it all in one script would be ideal.
Thanks!
So you have each door in each room? Try cross produce lacing as a start. 
Some rooms will vary. I did notice though that the list was incorrect. The first list you see 317 which is the room number followed by 17 numbers for each door mark in that room. However when I check the model there is only one door in this room and the rest are elsewhere. Not sure why it’s picking up the wrong ones.
I might adjust my search for all rooms to select model elements and filter for rooms so I can use one plan to test out first.
