This was interesting question so I posted it on unix.com, here is what Perderabo came up with....

This usual solution is something like, first write a wrapper script that will run somecommand only if the day of the month is 7 or less:


code:--------------------------------------------------------------------------------
#! /usr/bin/ksh
day=$(date +%d)
if ((day <= 7)) ; then
exec somecommand
fi
exit 1
--------------------------------------------------------------------------------


Then run the wrapper every Monday: "0 0 * * 1 wrapper".