Blocking The Screen

I have a business where I lend computers to customers for a certain amount for a specified number of hours. Mostly, customers rented my computers for gaming (Counter Strike, Quake 3....). I am maintaining 15 computers manually and I found it hard to keep track on the usage of the computers. What I want is that I'll make a program that is going to block the screen after the specified time (No. of minutes/hours) automatically, thus preventing the user to continue using the computer if his time is up. I created a program with such purpose by using the SetWindowPos API. I was successful when the user is only using windows apps. such as MS Office or the internet. But in terms of games, when it attempted to block the screen, all I get is a blinking screen and the game application prevailed. Is there any other API to use to solve this problem or is there any free program with such purpose whcih I can download?

DirectX and OpenGL (the APIs used in games) take over the screen real-estate when running. This means that only they can take up the screen. I suggest using Directdraw in fullscreen mode for the same purpose. That way since your program runs first, no other program can go on top of it.

If you show a message box (or inputbox for a password) as SystemModal, it will lock the whole system until you press OK or type a password :)

Combining the DX one with a modal password box can't lose :D

Hehe lol :p

Try this code, it should work:

VB Code:

'This happens when the user can't play anymore :p
 
Do While Password<>"the password"
    Password = InputBox("Your playing time has expired. Please type the correct password to continue or GET THE HELL OUTTA HERE!!!")
Loop

Please note that somewhere in the flags there should be one like "SystemModal" or something.