I haven't done it but I guess one way would be to include a registry setting in the Windows registry during the installation and check for existance of the same setting when the DLL is used/invoked and act appropriately.

>Does anyone have any advice on licensing a VFP DLL?
>I don't mean legal issues, but restricting use of the control only to machines that used our installation to install it.
>Any ideas or experiences would be appreciated! Thanks in advance!
>Mark