API: Close another Application

  To close another app, you need to know it's ClassName.   If you don't, then pick up the code from the article "Find ClassName of a Running App".  Then pass the classname as an argument to this function.

  Thanks to Dimitri Furman for pointing out the incorrect use of WaitForSingleObject API in the old sample.

'************** Code Start ***************
' This code was originally written by Dev Ashish.
' It is not to be altered or distributed,
' except as part of an application.
' You are free to use it in any application,
' provided the copyright notice is left unchanged.
'
' Code Courtesy of
' Dev Ashish
'
Private Const WM_CLOSE = &H10
Private Const INFINITE = &HFFFFFFFF

Private Declare Function apiPostMessage _
    Lib "user32" Alias "PostMessageA" _
    (ByVal hWnd As Long, _
    ByVal wMsg As Long, _
    ByVal wParam As Long, _
    lParam As Any) _
    As Long

Private Declare Function apiFindWindow _
    Lib "user32" Alias "FindWindowA" _
    (ByVal lpClassName As String, _
    ByVal lpWindowName As String) _
    As Long
    
Private Declare Function apiWaitForSingleObject _
    Lib "kernel32" Alias "WaitForSingleObject" _
    (ByVal hHandle As Long, _
    ByVal dwMilliseconds As Long) _
    As Long
    
Private Declare Function apiIsWindow _
    Lib "user32" Alias "IsWindow" _
    (ByVal hWnd As Long) _
    As Long
        
Private Declare Function apiGetWindowThreadProcessId _
    Lib "user32" Alias "GetWindowThreadProcessId" _
    (ByVal hWnd As Long, _
    lpdwProcessID As Long) _
    As Long
        
Function fCloseApp(lpClassName As String) As Boolean
'Usage Examples:
'   To close Calculator:
'       ?fCloseApp("SciCalc")
'
Dim lngRet As Long, hWnd As Long, pID As Long

    hWnd = apiFindWindow(lpClassName, vbNullString)
    If (hWnd) Then
        lngRet = apiPostMessage(hWnd, WM_CLOSE, 0, ByVal 0&)
        Call apiGetWindowThreadProcessId(hWnd, pID)
        Call apiWaitForSingleObject(pID, INFINITE)
        fCloseApp = Not (apiIsWindow(hWnd) = 0)
    End If
End Function
'************* Code End ***************