SendMessage给另一个程序

Private Const WM_LBUTTONDOWN = &H201
Private Const WM_LBUTTONUP = &H202
Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" (ByVal Hwnd1 As Long, ByVal Hwnd2 As Long, ByVal lpsz1 As String, ByVal lpsz2 As String) As Long
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Private Sub Form_Load()
Shell "calc.exe", vbNormalNoFocus
End Sub
Private Sub Command1_Click()
Dim Hwnd1 As Long
Dim Hwnd2 As Long
Hwnd1 = FindWindow("SciCalc", "计算器")
Hwnd2 = FindWindowEx(Hwnd1, 0, "Button", "1")
SendMessage Hwnd2, WM_LBUTTONDOWN, ByVal 0&, ByVal 0&
SendMessage Hwnd2, WM_LBUTTONUP, ByVal 0&, ByVal 0&
End Sub