unit Unit1;

interface

uses
  SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls,
  Forms, Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure FormKeyPress(Sender: TObject; var Key: Char);
  private
    AppInst: THandle;
    AppWind: THandle;
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

uses ShellAPI;


procedure SendShift(H: HWnd; Down: Boolean);
var vKey, ScanCode, wParam: Word;
    lParam: longint;
begin
  vKey:= $10;
  ScanCode:= MapVirtualKey(vKey, 0);
  wParam:= vKey or ScanCode shl 8;
  lParam:= longint(ScanCode) shl 16 or 1;
  if not(Down) then lParam:= lParam or $C0000000;
  SendMessage(H, WM_KEYDOWN, vKey, lParam);
end;

procedure SendCtrl(H: HWnd; Down: Boolean);
var vKey, ScanCode, wParam: Word;
    lParam: longint;
begin
  vKey:= $11;
  ScanCode:= MapVirtualKey(vKey, 0);
  wParam:= vKey or ScanCode shl 8;
  lParam:= longint(ScanCode) shl 16 or 1;
  if not(Down) then lParam:= lParam or $C0000000;
  SendMessage(H, WM_KEYDOWN, vKey, lParam);
end;

procedure SendKey(H: Hwnd; Key: char);
var vKey, ScanCode, wParam: Word;
    lParam, ConvKey: longint;
    Shift, Ctrl: boolean;
begin
  ConvKey:= OemKeyScan(ord(Key));
  Shift:= (ConvKey and $00020000) <> 0;
  Ctrl:= (ConvKey and $00040000) <> 0;
  ScanCode:= ConvKey and $000000FF or $FF00;
  vKey:= ord(Key);
  wParam:= vKey;
  lParam:= longint(ScanCode) shl 16 or 1;
  if Shift then SendShift(H, true);
  if Ctrl then SendCtrl(H, true);
  SendMessage(H, WM_KEYDOWN, vKey, lParam);
  SendMessage(H, WM_CHAR, vKey, lParam);
  lParam:= lParam or $C0000000;
  SendMessage(H, WM_KEYUP, vKey, lParam);
  if Shift then SendShift(H, false);
  if Ctrl then SendCtrl(H, false);
end;

function EnumFunc(Handle: HWnd; TF: TForm1): Bool; Far;
begin
  TF.AppWind:= 0;
  if GetWindowWord(Handle, GWW_HINSTANCE) = TF.AppInst then
    TF.AppWind:= Handle;
  result:= (TF.AppWind = 0);
end;

procedure TForm1.Button1Click(Sender: TObject);
var Text: Array[0..255] of char;
begin
  AppInst:= ShellExecute(Handle, 'open', 'notepad.exe', nil, '', SW_NORMAL);
  EnumWindows(@EnumFunc, longint(self));
  AppWind:= GetWindow(AppWind, GW_CHILD);
end;


procedure TForm1.Button2Click(Sender: TObject);
begin
  SendKey(AppWind, 'T');
  SendKey(AppWind, 'e');
  SendKey(AppWind, 's');
  SendKey(AppWind, 't');
end;

procedure TForm1.FormKeyPress(Sender: TObject; var Key: Char);
begin
  if AppWind <> 0 then SendKey(AppWind, Key);
end;

end.
///
Ah,这个嘛......正好在《DELPHI新闻组学习笔记》上看到一篇：
How to send [Alt]+[Down]?--------------发出一个Alt+Down 组合键

Re:
Use the keybd_event API function to fake keyboard events. Note that each
key down event needs a matching key up or you mess up the key state array.

  keybd_event( VK_MENU, MapVirtualKey( VK_MENU, 0 ), 0 , 0 );     // Alt down
  keybd_event( VK_DOWN, MapVirtualKey( VK_DOWN, 0 ), 0 , 0 );     // down arrow key down
  keybd_event( VK_DOWN, MapVirtualKey( VK_DOWN, 0 ), KEYEVENTF_KEYUP , 0 );  // down arrow key up
  keybd_event( VK_MENU, MapVirtualKey( VK_MENU, 0 ), KEYEVENTF_KEYUP , 0 );  // Alt key up

经本人试验，确实可行，另加补充：
Ctrl: VK_CONTROL
SHIFT:VK_SHIFT
TAB:  VK_TAB
'A':  byte('A')                (98-6-8 22:28)
/
(*
Converts a string of characters and key names to keyboard events and
passes them to Windows.

Example syntax:

SendKeys('abc123{left}{left}{left}def{end}456{left 6}ghi{end}789', True);

*)

Function SendKeys(SendKeysString : PChar; Wait : Boolean) : Boolean;
type
  WBytes = array[0..pred(SizeOf(Word))] of Byte;

  TSendKey = record
    Name : ShortString;
    VKey : Byte;
  end;