Private Declare Function CreateMutex Lib "kernel32" Alias "CreateMutexA" (ByVal lpMutexAttributes As Long, ByVal bInitialOwner As Long, ByVal lpName As String) As Long
Private Declare Function CloseHandle Lib "kernel32" (ByVal hObject As Long) As Long
'variable constant to match if the mutex exists
Private Const ERROR_ALREADY_EXISTS = 183&
'Application Variable Declarations
Public Const AppVer = "MyApp v1.1"
Public Function Test()
Dim Mutexvalue As Long
'*the following code would go in the starting function of your application
'either the main() or form_load() depending on how your application works
'Create an individual mutex value for the application
Mutexvalue = CreateMutex(ByVal 0&, 1, AppVer)
Debug.Print Mutexvalue
'If an error occured creating the mutex, that means it
'must have already existed, therefore your application
'is already running
If (Err.LastDllError = ERROR_ALREADY_EXISTS) Then
'Inform the user of running the same app twice
MsgBox "The application is already running."
'Terminate the application via the reference to it, its hObject value
CloseHandle Mutexvalue
Application.Quit acQuitSaveNone
End If
End Function
