how to update officescan server using Other update source.

I am creating a test environment with Trend Micro OfficeScan 7.3
software. Since my server should not be connected to outside world, so
for officescan server update I have to perform a manual update.

My plan
~~~~~~
Download updates from internet (using my laptop) and then I will copy
them to a server (internal web/ftp/file server of my test
environment).

Configure officescan server to download update from this server using
"Other update source" option under officescan server manual update.

I tried giving URL, where I copied update files, but officescan server
saying...
"The officescan server was unable to connect to the update source.
Verify proxy...."
if open same URL in IE, it is showing all the files listed in that
directory.

Can any one please advise me how should I handle this requirement and
what is the correct way of doing it?

Thank you very much for your time,
Kishore