Chris,
If you want to concentrate on your app instead of worrying about coding a 30-day trial, I would check out www.softwarekey.com . We and many other VFP developers have used them with good results. You just load up their DLL in your app. You can even automate unlocks over the internet once the app is payed for...
>Ho can i implement a block, which stops my program from running after a certain period of time or date. eg. a 30 Day trial period
>
>Chris