How can I tell if the program is already running?

[MartinLiss]

BTW why do you need to restrict it to one user at a time? Does it use some sort of common database or file?

[daydee]

I find this to be more versatile than App.PrevInstance.
IE: not only will it check for previous running instances but will bring the app to the foreground if it had been minimized.

You can easily modify it to do other stuff besides just that.
Please compile before running

Cheers!

'Form code
Option Explicit
 
Private Sub Form_Load()
    Call CheckAppPrevInstance
End Sub
 
'In a module
Option Explicit
 
Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" _
         (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function GetWindow Lib "user32" (ByVal hWnd As Long, _
         ByVal wCmd As Long) As Long
Private Declare Function OpenIcon Lib "user32" (ByVal hWnd As Long) As Long
Public Declare Function SetForegroundWindow Lib "user32" (ByVal hWnd As Long) As Long
Private Const GW_HWNDPREV = 3
 
Public Sub CheckAppPrevInstance()
    Dim OldTitle As String
    Dim ll_WindowHandle As Long
      
    'saving the current title in OldTitle variable
    'and changing the application title so it will not look for itself
    OldTitle = App.Title
    
    App.Title = "Dup instance"
    
    'finding the previous instance.
    ll_WindowHandle = FindWindow("ThunderRT6Main", OldTitle)
    'if there is no old instances of your application - exit.
        
    If ll_WindowHandle = 0 Then App.Title = OldTitle: Exit Sub
    
    'Find the window we need to restore
    ll_WindowHandle = GetWindow(ll_WindowHandle, GW_HWNDPREV)
     
    'Now restore it
    Call OpenIcon(ll_WindowHandle)
    'And Bring it to the foreground
    Call SetForegroundWindow(ll_WindowHandle)
             
    End
         
End Sub

[dglienna]

For another user, or on another machine?

[daydee]

For another user, or on another machine?

Sorry can't answer that one right now but will try it out first chance I get.

[szlamany]

I find this to be more versatile than App.PrevInstance.
IE: not only will it check for previous running instances but will bring the app to the foreground if it had been minimized.

.
.
.
    'finding the previous instance.
    ll_WindowHandle = FindWindow("ThunderRT6Main", OldTitle)
    'if there is no old instances of your application - exit.
.
.
.

Exactly what I was looking for - I was just wanting to change my App.PrevInstance code to actually find and bring the window to the front...

What is the ThunderRT6Main part mean? The OldTitle variable already contains the name of the app - so I'm unclear on Thunder part...