stderr & stdout to a file and the right exit code

Hi all,

I need to redirect stdout and stderr to a file in a ksh shell. That's not a problem. But I need also the correct exit code for the executed command. In the example below I redirect correctly the stdout & stderr to a file, but I have the exit code of tee command and not for the mv command.

The script:
#!/bin/ksh

(
mv files.log file.log
EXITSTATUS=$?
if [ ${EXITSTATUS} -ne 0 ]
then
exit ${EXITSTATUS}
fi
) 3>&1 1>&2 2>&3 |tee -a logfile
echo $?
echo "exit code" $EXISTATUS

here is the output:
mv: rename files.log to file.log: No such file or directory
0
exit code

here is the logfile:
mv: rename files.log to file.log: No such file or directory

Please, could anyone help me?
Thanks, bye

when piped the exit status $? would be effective with respect to the command that was executed at last--- tee in this case.

Just wondering if any one can help me understand how the below bolded code works.