Hi Lou,
Assuming you are referring to the following Download Cacher utility:
For reference, the command line options are available here:
If you are going to run this utility from a machine that is not a Relay (I’m assuming not the Root Server since it is air-gapped), then you’ll either need to supply the links to the files you wish to download, or the masthead file of the site you wish to download so that the utility can look up the urls. Using BES Support as an example, here is one potential way to run the utility:
BESDownloadCacher-5.8.3.exe -m bessupport.efxm -x R:\temp\cache\
You can find the masthead files (such as bessupport.efxm) of the various external sites in your environment from the actionsite folder of any Client (so long as at least one Client is subscribed to the site in question).