;;;Clean up on error
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(defun ERROR_ROUTINE (/)
(setq olderror *error*)
)

(defun *ERROR* (str_errmessage)
(princ str_errmessage)
(POSTRUN)
(setq *error* olderror)
(princ)
)

;;;Prepare
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(defun PRERUN (/)
(setq oldcmdecho (getvar "cmdecho"))
(setvar "cmdecho" 0)
(setq oldblipmode (getvar "blipmode"))
(setvar "blipmode" 0)
(command ".undo" "be")
)

;;;Restore
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(defun POSTRUN (/)
(command ".undo" "e")
(setvar "cmdecho" oldcmdecho)
(setvar "blipmode" oldblipmode)
(if oldosmode
(setvar "osmode" oldosmode)
)
)

;;;Main function
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(defun MB (/ ent_BreakFence cnt pnt_1 pnt_2 pnt_3 pnt_4 pnt_5 ss
ent_LineToBreak
)
(setq pnt_1 (getpoint "\nFirst point of break fence: "))
(if pnt_1
(progn
(setq pnt_2 (getpoint pnt_1 "\nSecond point of break fence: "))
(if pnt_2
(progn
(setq oldosmode (getvar "osmode"))
(setvar "osmode" 0)
(setq ss (ssget "_F" (list pnt_1 pnt_2) '((0 . "LINE"))))
(setq cnt 0)
(if (> (sslength ss) 0)
(repeat (sslength ss)
(setq ent_LineToBreak (entget (setq ent_BreakFence(ssname ss cnt)))
pnt_3 (cdr (assoc 10 ent_LineToBreak))
pnt_4 (cdr (assoc 11 ent_LineToBreak))
pnt_5 (inters pnt_1 pnt_2 pnt_3 pnt_4 T)
)
(if pnt_5
(command "_.break" ent_BreakFence pnt_5 pnt_5)
)
(setq cnt (1+ cnt))
)
)
)
)
)
)
)

;;;Control function
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(defun C:MB ()
(PRERUN)
(ERROR_ROUTINE)
(MB)
(POSTRUN)
)

(prompt "\nType MB to run..")