AutoCAD Visual LISP / AutoLISP :: Program Loop To Draw Lines With Rubberband

i am writing something that will draw consecutive lines with a rubberband to be used as a leader from a block's insertion point.  this:

(WHILE
 (SETQ LN (GETPOINT "
Select Next Point (ENTER to Finish) : "))
 (COMMAND "LINE" (GETVAR "LASTPOINT") LN "")
)   

works, but does not include the rubber band.  i tried:

(WHILE
 (SETQ LP (GETVAR "LASTPOINT"))
 (SETQ LN (GETPOINT LP "
Select Next Point (ENTER to Finish) : "))
 (COMMAND "LINE" LP LN "")
)   

which includes the rubberband, but will not exit the loop. The last break source in VLIDE shows that  

(GETPOINT LP "
Select Next Point (ENTER to Finish) : ") is casuing an error.  Placing
 (SETQ LP (GETVAR "LASTPOINT"))

 outside the loop causes all lines to be drawn from the same point rather than the endpoint of the previous line.