Tank you both,
As a newbie in B4A, I've just now read the "Started", "Language", "Designer" and "B4XPages" Booklets :'-) and find a lot of useful answers ...
I'm printing the 77 pages of the "Custom View" and will learn it now ,on your advice.
Coming from Pascal with "Delphi/Embarcadero" I like the "DRY" principle tip "Never write 2 times the same code in a project => write a subroutine, never use 2 times the same subroutine in 2 projects => write a Library" (Add a Lib to a Project is precisely called a "Use" in Pascal)
And according with Erel, I appreciate the "OpenSource" principle of the B4XLIB : easy sharing => easy learning => and sharing back ...
About SubRoutines : I suppose it's not possible to create a Private SubRoutine in another SubRoutine because Sub in Basic has no explict "Begin" instruction ?
***{:- Kénavo