Restricting sftp commands

[m l]

I've install OpenSSH_4.2p1 with RSSH on Solaris 10. It only accept "sftp" . 
I block SSh and the others.
But the user still able to do commands like "chmod" "put" ,"get" 
etc......under sftp.
Is there any way, when the user is in sftp prompt, to limit him to only use 
for example "PUT" command ?

Martin
"Do, Or do not. There is no try."  -YODA-