I don't think that the NT batch language is robust enough to get that job done.
Within SQL Server, DTS is probably the simplest answer. You can combine Active-X script (essentially VBA) with "canned" FTP tasks to make this process pretty simple.
You could install a more powerful scripting language like Perl or PHP. They include the tools needed to make this relatively simple. This is probably the most generic answer, since you can run both Perl and PHP on either Windows or Unix, so the commonality will probably make things much simpler.
If you want to do this at a still lower level, you could code it in
VB, VC, or another language.
-PatP