I tried to modify this routine (to rename all Layout Tabs)
(vl-load-com)
(defun RenLay ( kword / n)
(setq n 1)
(vlax-for x (vla-get-Layouts (vla-get-ActiveDocument (vlax-get-acad-object)))
(if (not (eq (strcase (vla-get-name x)) "MODEL"))
(vla-put-Name x (strcat kword (itoa...