@echo off
set /p ext=Extension?
set /p cant=Cantidad final de caracteres?
call :len %ext%
set /a cnt2=%a%+%cant%
for %%a in (*.%ext%) do call :cll %%a
exit
:cll
set name=%1
call :len %1
if /I %a% geq %cnt2% (
	call set newn=%%name:~0,%cant%%%.%ext%
	ren %name% %newn%
)
goto :EOF
 
:len
if %1'==' goto :EOF
set w=%1
set a=0
set bol=0
:lp
call :cnt "%%w:~%a%,1%%" %a%
if %bol%==1 goto :EOF
set /a a=%a%+1 
goto lp
:cnt
set cur=%1
set len=%2
if %cur%a==""a (
	echo %len%
	set bol=1
)
goto :EOF

@echo off
for %%a in (*.xls) do call :cll %%a
pause
exit
 
:cll
set name=%1
set t=%name:~-8%
call set fin=%%name:%t%=%%
ren %name% %fin%.xls
goto :EOF