selection from a list

I know that this is possible but not completly sure how to locate the lisp, macro, etc...

I have several block that I would like to select from with one command.  

example

(defun cImage may be NSFW.
Clik here to view.nl()(command -insert" "pnl" select panel size from list...

And from there I would type in "12" for 12 space panel, "18" for 18 space panel, etc.  

need it for 12, 18, 24, 36, 48.

Image may be NSFW.
Clik here to view.Image may be NSFW.
Clik here to view.Image may be NSFW.
Clik here to view.Image may be NSFW.
Clik here to view.Image may be NSFW.
Clik here to view.

Image may be NSFW.
Clik here to view.