Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

 {With keybd_event API}

 procedure PostKeyExHWND(hWindow: HWnd; key: Word; const shift: TShiftState;
   specialkey: Boolean);
 {************************************************************ 
 * Procedure PostKeyEx 
 * 
 * Parameters: 
 *  hWindow: target window to be send the keystroke 
 *  key    : virtual keycode of the key to send. For printable 
 *           keys this is simply the ANSI code (Ord(character)). 
 *  shift  : state of the modifier keys. This is a set, so you 
 *           can set several of these keys (shift, control, alt, 
 *           mouse buttons) in tandem. The TShiftState type is 
 *           declared in the Classes Unit. 
 *  specialkey: normally this should be False. Set it to True to 
 *           specify a key on the numeric keypad, for example. 
 *           If this parameter is true, bit 24 of the lparam for
 *           the posted WM_KEY* messages will be set.
 * Description:
 *  This procedure sets up Windows key state array to correctly
 *  reflect the requested pattern of modifier keys and then posts
 *  a WM_KEYDOWN/WM_KEYUP message pair to the target window. Then
 *  Application.ProcessMessages is called to process the messages
 *  before the keyboard state is restored.
 * Error Conditions:
 *  May fail due to lack of memory for the two key state buffers.
 *  Will raise an exception in this case.
 * NOTE:
 *  Setting the keyboard state will not work across applications
 *  running in different memory spaces on Win32 unless AttachThreadInput
 *  is used to connect to the target thread first.
 *Created: 02/21/96 16:39:00 by P. Below
 ************************************************************}

 type
   TBuffers = array [0..1] of TKeyboardState;
 var
   pKeyBuffers: ^TBuffers;
   lParam: LongInt;
 begin
   (* check if the target window exists *)
   if IsWindow(hWindow) then
   begin
     (* set local variables to default values *)
     pKeyBuffers := nil;
     lParam := MakeLong(0, MapVirtualKey(key, 0));

     (* modify lparam if special key requested *)
     if specialkey then
       lParam := lParam or $1000000;

     (* allocate space for the key state buffers *)
     New(pKeyBuffers);
     try
       (* Fill buffer 1 with current state so we can later restore it.
          Null out buffer 0 to get a "no key pressed" state. *)
       GetKeyboardState(pKeyBuffers^[1]);
       FillChar(pKeyBuffers^[0], SizeOf(TKeyboardState), 0);

       (* set the requested modifier keys to "down" state in the buffer*)
       if ssShift in shift then
         pKeyBuffers^[0][VK_SHIFT] := $80;
       if ssAlt in shift then
       begin
         (* Alt needs special treatment since a bit in lparam needs also be set *)
         pKeyBuffers^[0][VK_MENU] := $80;
         lParam := lParam or $20000000;
       end;
       if ssCtrl in shift then
         pKeyBuffers^[0][VK_CONTROL] := $80;
       if ssLeft in shift then
         pKeyBuffers^[0][VK_LBUTTON] := $80;
       if ssRight in shift then
         pKeyBuffers^[0][VK_RBUTTON] := $80;
       if ssMiddle in shift then
         pKeyBuffers^[0][VK_MBUTTON] := $80;

       (* make out new key state array the active key state map *)
       SetKeyboardState(pKeyBuffers^[0]);
       (* post the key messages *)
       if ssAlt in Shift then
       begin
         PostMessage(hWindow, WM_SYSKEYDOWN, key, lParam);
         PostMessage(hWindow, WM_SYSKEYUP, key, lParam or $C0000000);
       end
       else
       begin
         PostMessage(hWindow, WM_KEYDOWN, key, lParam);
         PostMessage(hWindow, WM_KEYUP, key, lParam or $C0000000);
       end;
       (* process the messages *)
       Application.ProcessMessages;

       (* restore the old key state map *)
       SetKeyboardState(pKeyBuffers^[1]);
     finally
       (* free the memory for the key state buffers *)
       if pKeyBuffers <> nil then
         Dispose(pKeyBuffers);
     end; { If }
   end;
 end; { PostKeyEx }

 // Example: 

procedure TForm1.Button1Click(Sender: TObject);
 var
   targetWnd: HWND;
 begin
   targetWnd := FindWindow('notepad', nil)
     if targetWnd <> 0 then
     begin
       PostKeyExHWND(targetWnd, Ord('I'), [ssAlt], False);
   end;
 end;