if you always want to have the same path, you could also use subst (CMD command).For example:

subst <usbdriveletter>:\myportablesoftware v:
[download]

like that you could "remount" a directory as an drive letter. If you pick a higher drive letter it's likely that it never will be taken. If you configure your software for v: it will always work, you'll only have to call subst with a correct directory before trying to execute the scripts.