probably more than you need but ........
Code:
(defun get-active-doc ()
(vla-get-activedocument (vlax-get-acad-object))
)
(defun get-blk-names2 (/ blk layout_blks
xref_blks blks blk_name_list
)
(vlax-for blk (vlax-get-property (get-active-doc) 'Blocks)
(cond ((= (vlax-get-property blk 'IsLayout) :vlax-true)
(setq layout_blks
(cons (vlax-get-property blk 'Name) layout_blks)
)
)
((= (vlax-get-property blk 'IsXRef) :vlax-true)
(setq xref_blks
(cons (vlax-get-property blk 'Name) xref_blks)
)
)
(T (setq blks (cons (vlax-get-property blk 'Name) blks)))
)
)
(setq blk_name_list (list layout_blks xref_blks blks))
)
(setq blst (get-blk-names2))