I can't execute a script in crontab

[Yavuz Maşlak]

I use freebsd7.2

I wish to send a file using crontab as periodic. I have a script to send the 
file.
When I am root, I can execute my script, but I can't execute the script 
using crontab.
How can I run it ?

cat myscript
/usr/bin/scp -i /root/.ssh/id_rsa.pub /root/cpfile 
root at 192.168.10.9:/var/cpfile

Thanks