Option 1:
Change your shipping app to have browser or automatic ftp support built in. This way when date expires, program will automatically launch ftp/browser to your site, check that they can continue using program and then transfer new date program to them in the correct location.
My Advice: Shipping in week you say. I DON'T THINK SO!
Option 2:
Change your shipping app to have a message box or whatever to show them your url, (have seen here how you can embed a link on form) when their time is up. On your sever using asp (java, java script, vbscript) verify that they have rights to continue using program. Give them a link to download new file and tell them where to stick it, or zipit so it extracts where it needs to be.
My Advice: Real quick on both sides. I personally would use this approach, given your shipping in a week. ASP stuff is real easy, can even have all this data driven on server side for verification and/or have the server build the new file before downloading to them.
Option 3:
Put a card in the shipping box with your url and tell them to go there if they ever have any problems. Put link to new file and have them download, if they ever find you.
My Advice: Save the money don't buy the server. Just give them a phone number and/or snail mail address.
Option 4:
Wait until someone else gives you better Advice.
My Advice: Patients