Hi. =)
It sounds like you're on Windows. I'm not much of a Windows guru, but doing this in UNIX is rather straightforward -- maybe you can convert my ideas into a usable batch file -- of course, it would be great if you could share your results with the group too...
If you have a text file, which contains a list of OnDemand Load ID's, one per line, you would use the following script in UNIX's Korn Shell (ksh) or Bourne Again Shell (bash):
for i in `cat load-id-file`
do
arsadmin unload -h hostname -u userid -p password -L $i
done
UNIX Shell scripting has a few conventions you might not be familiar with...
for is a looping structure.
` (backtick) characters execute the command within them
cat is analogous to Windows' 'type' command.
do and done enclose a loop.
If this is helpful, I'm sure the rest of the users would be interested to see what you come up with.