Very happy with the code mr. Roy_43 provided
Works like a charm!
Using AutoCAD
(defun c:Unpurg (/ enm lst ptrs)
(setq lst '("1" "2" "3")) ; Laagnamen.
(foreach nme lst
(if (setq enm (tblobjname "LAYER" nme))
(setq ptrs (cons (cons 340 enm) ptrs))
)
)
(gc:SetXrecData
(gc:GetOrCreateExtDict (cdr (assoc 330 (entget (tblobjname "LAYER" "0")))))
"LAYER_UNPURGE"
ptrs
)
(princ)
)
Using BricsCAD
(defun gc:GetOrCreateExtDict (ent / dict)
(cond
((cdadr (member '(102 . "{ACAD_XDICTIONARY") (entget ent))))
((setq dict (entmakex
'((0 . "DICTIONARY") (100 . "AcDbDictionary"))
)
)
(entmod (append (list '(102 . "{ACAD_XDICTIONARY")
(cons 360 dict)
'(102 . "}")
)
(entget ent)
)
)
dict
)
)
)