I thought this was worth coding for our own use, SO ....
Have a play with this.
(defun c:Split_Dims (/ sel newpt ent edata elist)
;; codehimbelonga KerryBrown@theSwamp 2010.05.28
(if (and (setq sel (entsel "\nSelect Dimension to Split."))
(setq newpt (getpoint "\Select new Dim Point"))
)
(progn (setq ent (car sel)
edata (entget ent)
elist (vl-remove-if
'(lambda (pair)
(member (car pair)
(list -1 2 5 102 310 300 330 331 340 350 360 410)
)
)
edata
)
)
(entmod (subst (cons 14 newpt) (assoc 14 elist) edata))
(entmakex (subst (cons 13 newpt) (assoc 13 elist) elist))
)
)
(princ)
)
Code added: