;TIP552.LSP   Dimension to Wall Centrelines   (c)1990, Jeffrey Morris
(defun btwn ( / ENT1 ENT2)
  (setq ENT1 (getpoint "First line: ")
        ENT2 (getpoint "Second line: ")
  )
  (list
    (+ (car ENT1)(* 0.5 (- (car ENT2)(car ENT1))))
    (+ (cadr ENT1)(* 0.5 (- (cadr ENT2)(cadr ENT1))))
    (+ (caddr ENT1)(* 0.5 (- (caddr ENT2)(caddr ENT1))))
  )
)