How to automate password change using WinSCP

Hi I'm new to WinSCP, using version 5.7.7.0 and I was able to use .Net & Com library to do basic SFTP operations such as upload, download, make directory, list directory.

I'm not sure how I can automate password change.

I was trying to use session.ExecuteCommand("passwd oldpassword newpassword newpassword"); and got an error as below.

Command 'passwd oldpassword newpassword newpassword'
failed with return code 6 and error message
usage:
passwd [-r files | -r nis | -r nisplus | -r ldap] [name]
passwd [-r files] [-egh] [name]
passwd [-r files] -sa

Can some one please explain me how I can do the password change using ExecuteCommand or terminal ssh scripts?

Thanks
Pubudu

The passwd is explicitly made not to be automatable. For a good reason.