You may configure the crontab job to run every sat via a script that will do something like:
if test -f /mydir/ranlastweek
then
rm /mydir/ranlastweek
exit
fi
touch /mydir/ranlastweek
other commands to run the job
This is a logic to test if the job was ran last week, if yes then just remove the file and exit, other wise create the file and run the job.