How are you creating your pipes?
If you are using Advanced Framework Extension, then the parameters are in there as BUW_xxxx, I think length is one of them.
If you are just creating pipes in a family table or standalone, you can rename the driving parameter to Length and use that in a table.
I did create a table that shows lengths for an AFX developed structure of steel channels.
This assembly used tubing, not pipes, but you get the idea.
