The -S flag allows encfs4win to read passwords from stdin on Windows. Here we use a keyfile to script the mount of a reversed encfs share on Windows.

type C:\encfs-key.txt|C:\encfs4win\encfs.exe -S --reverse C:\Users\Will\Documents C:\Users\Will\Encrypted\Documents

You could also echo the password to the script

echo the-password|C:\encfs4win\encfs.exe -S --reverse C:\Users\Will\Documents C:\Users\Will\Encrypted\Documents