VB后台按键

算了,发个完整的代码给你吧,自己改.记得常数要定义.
当然,PostMessage的最后一个参数用0也可以,下面是完整的.

窗体代码：
Private Sub Form_Load()
Dim hwnd As Long
hwnd = &HXXXX 'XXXXX表示记事本编辑框的句柄
PostMessage hwnd, WM_KEYDOWN, VK_A, MakeKeyLparam(VK_A, WM_KEYDOWN) '按下A键
PostMessage hwnd, WM_CHAR, Asc("A"), MakeKeyLparam(VK_A, WM_KEYDOWN) '输入字符A
PostMessage hwnd, WM_UP, VK_A, MakeKeyLparam(VK_A, WM_UP) '释放A键
End Sub
模块代码：
Declare Function PostMessage Lib "user32" Alias "PostMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Declare Function MapVirtualKey Lib "user32" Alias "MapVirtualKeyA" (ByVal wCode As Long, ByVal wMapType As Long) As Long

Public Const WM_KEYDOWN = &H100
Public Const WM_KEYUP = &H101
Public Const WM_CHAR = &H102
Public Const VK_A = &H41

Function MakeKeyLparam(ByVal VirtualKey As Long, ByVal flag As Long) As Long
Dim s As String
Dim Firstbyte As String 'lparam参数的24-31位
If flag = WM_KEYDOWN Then '如果是按下键
Firstbyte = "00"
Else
Firstbyte = "C0" '如果是释放键
End If
Dim Scancode As Long
'获得键的扫描码
Scancode = MapVirtualKey(VirtualKey, 0)
Dim Secondbyte As String 'lparam参数的16-23位，即虚拟键扫描码
Secondbyte = Right("00" & Hex(Scancode), 2)
s = Firstbyte & Secondbyte & "0001" '0001为lparam参数的0-15位，即发送次数和其它扩展信息
MakeKeyLparam = Val("&H" & s)
End Function

常量声明了吗？timer1.enabeld=true
timer1.interval=100有吗？

SendKeys "{F4}"

这句足够了

你说的后台 是 类似qq那种 c+a+z 吧

这东西要hook 用api写的

代码 可以自己搜索 不过一般都有小问题