proberbly long winded but i did it this way and it worked so thanks to all that helped but if there is an easier way can someone elaborate thanks....
#!/bin/bash
echo "enter name"
read name
echo "enter subject"
read sub
echo "enter message"
read mess
echo "mail to"
read letter
echo "please enter day of month to send mail"
read day
echo "0 20 $day * * /home/mailshot/sendmail -f
sales@blah.co.uk -t "$letter" -m "$mess" -u "$sub"" > /home/mailshot/1.txt
echo "0 20 $day * * /home/mailshot/sendmail -f
sales@blah.co.uk -t "jerry@blah.co.uk" -m "$mess" -u "$name $sub"" > /home/mailshot/2.txt
echo "0 20 $day * * /home/mailshot/sendmail -f
sales@blah.co.uk -t "phil@blah.co.uk" -m "$mess" -u "$name $sub"" > /home/mailshot/3.txt
a=`cat /home/mailshot/1.txt`
b=`cat /home/mailshot/2.txt`
c=`cat /home/mailshot/3.txt`
z=`cat /home/mailshot/mail.cron`
# make Filedescriptor(FD) 6 a copy of stdout (FD 1)
exec 6>&1
# open file "mail.cron" for writing
exec 1>/home/mailshot/mail.cron
# produce some content
echo "$z"
echo "$a"
echo "$b"
echo "$c"
# close file "mail.cron"
exec 1>&-
# make stdout a copy of FD 6 (reset stdout)
exec 1>&6
# close FD6
exec 6>&-
crontab /home/mailshot/mail.cron
rm -rf /home/mailshot/1.txt
rm -rf /home/mailshot/2.txt
rm -rf /home/mailshot/3.txt
exit 0