Private Declare Function FindWindows Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function PostMessage Lib "user32" Alias "PostMessageA" (ByVal hWnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Private Const WM_CLOSE = &H10

Private Sub Command1_Click()
'winhwnd = FindWindows("Windows 任务管理器", vbNullString) '知道窗口类名，关闭
winhwnd = FindWindows(vbNullString, "Microsoft Word") '知道窗口标题，关闭
Call PostMessage(winhwnd, WM_CLOSE, 0&, 0&)
End Sub