sadly the 'runas' command won't let you pipe the password as it is as sidewinder has said and locked down as a security feature.
someone else asked this not to long ago. I think they got it working by using pstools, psexec is designed to run apps on remote machines, but i see no reason why you couldn't get it run on the local machine.
psexec will allow to hardcode a password into the batch.
hope it helps.