Ok i see now what you mean.
here is AutoDB command to do what you want
first you be asked to specify the 1st dimension line point: you need to pick the 1st point to the left of your base line. than pick the 2nd point to the right (turn ortho on) over the last line
the lisp will select all lines (only lines and if there are other lines remove them) by "Fence"
than the dimensions will be drawn
improve your dimension style so the outcome will be more readable.
if this suits you, mark it as solusion.
enjoy
moshe
(defun c:AutoDB (/ p0 p1 ss lst^ p13 item0 item1)
(setvar "cmdecho" 0)
(command ".undo" "_begin")
(if (and
(setq p0 (getpoint "\nSpecify first dimension line point: "))
(setq p1 (getpoint p0 "\nSpecify second dimension line point: "))
(setq ss (ssget "F" (list p0 p1) '((0 . "line"))))
)
(progn
(setq lst^ (vl-sort (ssnamex ss) (function (lambda (item0 item1) (< (distance p0 (cadr (last item0))) (distance p0 (cadr (last item1))))))))
(setq item0 (car lst^) item1 (cadr lst^))
(command "._dimlinear" (setq p13 (cadr (last item0))) (cadr (last item1)) (polar p13 (/ pi 2) (* (getvar "dimtxt") (getvar "dimscale")))
"._dimtedit" "_last" "_right")
(foreach item1 (cddr lst^)
(command "._dimbaseline" (cadr (last item1)) "" ""
".dimtedit" "_last" "_right")
); foreach
); progn
); if
(command "._undo" "_end")
(setvar "cmdecho" 1)
(princ)
)