程序代码：

Option Explicit
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 Declare Function MapVirtualKey Lib "user32" Alias "MapVirtualKeyA" (ByVal wCode As Long, ByVal wMapType As Long) As Long
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 Const WM_KEYDOWN = &H100
Private Const WM_KEYUP = &H101
Private Const WM_CHAR = &H102
Private Sub Form_Click()
Dim a As Long
a = PostMessage(Text1.hwnd, WM_KEYDOWN, vbKeyA, 0&)
a = PostMessage(Text1.hwnd, WM_KEYUP, vbKeyA, 0&)
End Sub