I personally think its a good idea - a nice way to limit users to creating standardised layers when required.
I should say that the '1234' example was just that, an example.
So, back to more pressing matters: you will need to create the dialog using DCL, this can be a separate file, or a file created by the LISP program (I prefer the latter).
Are you sourcing the lists for the dialog from an external file, or hard-coding them into the program?
Creating the layer is the easy part of this task, there are many ways this can be done, using the command, AutoLISP, or Visual LISP.