DOS automated user input

I want to run vnc from a command using the following syntax (see below) so that I would not have be sitting at my computer when the "runas" command prompts me for my password. I have not been successful in finding a workaround for the runas command, since it won't accept a password parameter. Any ideas?

cmd /c echo [password] | runas /user:[username] [vnc.exe]

Thanks,
cappaberra