You could also look into a thin-client solution if this is a current windows application. To turn them off would just require suspending their Windows account.

Wayne

>Hi Wayne,
>
>>Could you make it a subscription service on the internet - ie, web based? >Then just enable/disable the user's account as necessary?
>>
>>If not, a web service would seem to be a good fit for this - have your >application allow the user to enter payment information then send it to a >web service (securely). The web service provides a key/date that you >encrypt to allow the program to run.
>
>I don't really have a clue where to start with either of these, but I'll do my homework and see what I come up with.
>
>The web service seems like a good fit.
>
>Mel Cummings