Check for Running Instance of an application

Hi,
I'm trying to keep from running multiple instances of the rundll32.exe (open with dialog.). I've read alot of topics on the forum and they all seem to be about app.prevInstance, but can't find one dealing with outside applications. Can anybody point me in the right direction? Thanks alot, Rick

Shell ("rundll32.exe shell32.dll,OpenAs_RunDLL " & strFullName)

VB Code:

Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
 
Private Sub Command1_Click()
    Dim WinWnd As Long
    WinWnd = FindWindow(vbNullString, strFullName)
    If WinWnd = 0 Then
       MsgBox "Application Not Running"
    Else
       MsgBox "Application Already Running"
    End If
End Sub

Regarding App.PrevInstance
That is only for your own current application.

So in your Main() or Form_Load() Sub you would check for App.PrevInstance, and that would tell you if this app is already running or not.

Thanks for the replies. Thanks Hack, that is perfect!:D