Visual Basic 6 Desparately need help!

I'm I'm running VB 6. And I want to compile an exacutable that is not allowed to load two copies simoteniously. In 5 there was a check box in properties that just solved this problem. I seem to have no such luck in 6. Am I missing something? Is there an easy way I can code it myself? I was thinking if I could find a away to send a message from one exe to another. All I would do is when the second was trying to load send some messages to and from that turns the second off and gives the first focus. Anybody have any ideas.