Change Layout name to filename 64 characters long

Is there a way to change a current Layout name to a filename 64 characters long?

As far as I know I can take off the extension of the filename by using the lisp below. That's taking off 4 characters from the right of the filename. I'm looking for a lisp that would allow me to rename up to 64 characters long from the left of the filename.

Here's what I have so far:

(defun C:loRe ()
(setq ctabname(substr (getvar "dwgname") 1 (- (strlen (getvar "dwgname")) 4)))
(command ".layout" "R" "" ctabname)
(princ)
)

 

try -
(vl-load-com) ; only required once per session
(setq ctabname (vl-filename-base (getvar "dwgname")))

lisp below. That's taking off 4 characters from the right of the filename.
I'm looking for a lisp that would allow me to rename up to 64 characters
long from the left of the filename.

 

Okay, here's what I'm trying to do.
Example:
Here's my file name at 81 character's long:
MA-G-500020-1-12KV NO.3 XFMR PCB B3273 MA342 AC-DC SCHEMATIC & WIRING DIAGRAM.dwg

Here's my file name at 64 characters long:
MA-G-500020-1-12KV NO.3 XFMR PCB B3273 MA342 AC-DC SCHEMATIC & W

I'm looking for a lisp that would rename my layout to a maximum of 64 characters long (it can't exceed 64 characters) I have alot of file names that are over 64 characters long. Any ideas?

 

Your xref layer names must be long....

I would look for ways to shorten your file names.
MA-G-500020-1-12KV #3 XFMR PCB B3273 MA342 AC-DC Sch-Wire Dia.dwg

 

(defun C:loRe ()
(vl-load-com)
(setq ctabname (substr (vl-filename-base (getvar "dwgname")) 1 64))
(command ".layout" "R" "" ctabname)
(princ)
)

 

Exactly what I was looking for! Thanks for your understanding.