passwd envi. variable

I read from smbmount manual pages: -- password=<arg> - specifies the SMB password. If this option is not given then the environment variable PASSWD is used. If it can find no password smbmount will prompt for a passeword, unless the guest option is given. -- How can I use this passwd variable? I login with user xxx and password yyy. Now I want to mount smth so that I don't have to enter username (possible) and password anymore... Is it possible?