Enhance ddefine's function that creates a default screen 0 so that instead, it will prompt for a screen #/name, and a starting field #. It can then run as it has (using the same functionality to determine how to fit as many fields on the screen as possible), except creating the specified screen #/name and respecting the starting field number.
Also, it should always prompt before overwriting any screen #/name.
This entire new functionality would better be place in define screens, where it can always be used without locking out other users.