How do I supply a password and decrypt on NT

[Clough, Samuel]

I'm running gnupg on NT (not by choice).  Anyway, I need to be able to
automate encryption and decryption.  What should I use to do this and is it
possible?

I can decrypt using:
gpg --decrypt source.txt > output.txt

But is there a way around being prompted for a password?
I tried the --passphrase-fd option, but cannot find a way to assign a file
descriptor in windows or to feed it someone through the standard input.  Is
there a way to do this in windows?  

Can I do something by running in batch mode?  I don't have a good
understanding of running that way and have not found documentation for
decryption in batch mode.

I need something automated so I'm basically hacking my way to a com
component that has api calls to send a dos command and return the output.  I
then parse the output to see if it succeeded.  The problem is I need to get
around the password prompt on decryption.  Any help would be very much
appreciated.  I've tried everything in the man pages and can't see a way to
do this on windows.