Cant set width of each custom data viewer element dynamicly

Hi!

I’m trying to enter the width of the data viewr list element as a binding, but cant figure out if this has to be string or number. I set this as number and also tried with percentage but when i preview the app crashes.

Does anybody knows? I want to make a pyramid-ish data viewer list so depending on category the row has a rel width

Captura de pantalla 2021-03-14 a las 12.29.49

thanks for the help!