Checking whether my program is running and to terminate the second attempt

Hi, I am trying to check whether my program is running and if so when other users attempt to run the program, it should terminate, don't let the program run and pop up the already form window which i have been already hidden.

I have tried [ if (app.PrevInstance = true) then
End
Else
Load frmMain
EndIf ]

And here what happens was that its checking itself and didn't even run for the first time. Please help me.

Thank you in advance.
:(

See attached file for all instruction.

Regards.

hi thanx for the codes that you have attached..

now my question is..is "ThunderRT6Main" the window's name? and would it be ok if I just add the codes in the Module.?:confused: