You can use the KeyChk function to check for the presence of your Key as often as you like. This will make it much more difficult to move the Key while your protected program is running.
For example, most protected programs call KeyChk when they are first started. As the program runs, it might call KeyChk to verify the presence of your Key every time the User does a "Print" or "Save" function. Or, some protected programs just call KeyChk every 5-10 minutes.
Each time you call KeyChk, you will be verifying that your Key has not been moved to another computer.