Well, you could use a new selection set and add each new item to the selection set with ssadd....
Create an empty selection set when the proggie starts:
(setq newsset (ssadd))
After each line segment is created:
(setq newsset (ssadd (entlast) newsset))
When you need to operate on the lines later, you have an entire selection set....
OR
when the proggie starts grab the last entity in the drawing
(setq elast (entlast))
After the last line is created
(setq newsset (ssadd))
(while (setq elast (entnext elast))
(setq newsset (ssadd elast newsset))
)
good luck