As long as it doesn't last longer than 24hours...
@echo off
set starttime=%TIME%
set startcsec=%STARTTIME:~9,2%
set startsecs=%STARTTIME:~6,2%
set startmins=%STARTTIME:~3,2%
set starthour=%STARTTIME:~0,2%
set /a starttime=(%starthour%*60*60*100)+(%startmins%*60*100)+(%startsecs%*100)+(%startcsec%)
:TimeThis
ping localhost
set endtime=%time%
set endcsec=%endTIME:~9,2%
set endsecs=%endTIME:~6,2%
set endmins=%endTIME:~3,2%
set endhour=%endTIME:~0,2%
if %endhour% LSS %starthour% set /a endhour+=24
set /a endtime=(%endhour%*60*60*100)+(%endmins%*60*100)+(%endsecs%*100)+(%endcsec%)
set /a timetaken= ( %endtime% - %starttime% )
set /a timetakens= %timetaken% / 100
set timetaken=%timetakens%.%timetaken:~-2%
echo.
echo Took: %timetaken% sec.