Execute a SSH command

Hi to all, I need to execute a command in a remote machine throw ssh, but that command only can be executed by one user, for example xpto. This and all other users (except root) cannot execute commands in the remote machine with ssh except this particular user for this particular command. Resuming, only the user xpto can execute only this command with ssh. All others cannot execute any command. Any help ? Any reference ? Thanks to all in advance Joao Reis