(Entmod)ing an mlstyle

I am using the following code to try to change all mline entities to bylayer
color. I am getting nil returned on all entmods except for the "Standard"
style. This is my first time dealing with dictionarys and must be missing
something key.
(defun temp ()
(setq named_object (entget (cdr (assoc -1 (dictsearch (namedobjdict)
"acad_mlinestyle")))))
(repeat (length named_object)
(if (= (car (car named_object)) 350)
(progn
(setq ml_style (entget (cdr (car named_object))))
(repeat (+ 1 (setq ml_style_count (- (length ml_style) 1)))
(if (= (car (nth ml_style_count ml_style)) 62)
(setq ml_style (subst (cons 62 256) (nth ml_style_count
ml_style) ml_style))
)
(setq ml_style_count (- ml_style_count 1))
)
(princ (entmod ml_style))
)
)
(setq named_object (cdr named_object))
)
)
Any direction is appreciated.
Thanks
Cliff