VB 回调函数问题

*模块
Private Declare Function CallNextHookEx Lib "user32" (ByVal hHook As Long, ByVal nCode As Long, ByVal wParam As Long, lParam As Any) As Long
Private Declare Function SetWindowsHookEx Lib "user32" Alias "SetWindowsHookExA" (ByVal idHook As Long, ByVal lpfn As Long, ByVal hmod As Long, ByVal dwThreadId As Long) As Long
Private Declare Function UnhookWindowsHookEx Lib "user32" (ByVal hHook As Long) As Long
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, Source As Any, ByVal Length As Long)
Private Type PKBDLLHOOKSTRUCT
vkCode As Long
scanCode As Long
flags As Long
time As Long
dwExtraInfo As Long
End Type
Private Const WM_KEYDOWN = &H100
Private Const WM_SYSKEYDOWN = &H104
Private Const WM_KEYUP = &H101
Private Const WM_SYSKEYUP = &H105
Private Const HC_ACTION = 0
Private Const WH_KEYBOARD_LL = 13
Private lngHook As Long
Public Function HotKey(ByVal nCode As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Dim p As PKBDLLHOOKSTRUCT
If nCode = HC_ACTION Then
Select Case wParam
Case WM_KEYDOWN, WM_SYSKEYDOWN
Call CopyMemory(p, ByVal lParam, Len(p))
If p.vkCode = vbKeyA Then
MsgBox "你按下了A键"
End If
Case Else
End Select
End If
Call CallNextHookEx(WH_KEYBOARD_LL, nCode, wParam, lParam)
End Function
Public Sub HooK()
lngHook = SetWindowsHookEx(WH_KEYBOARD_LL, AddressOf HotKey, App.hInstance, 0)
End Sub
Public Sub UnHooK()
Call UnhookWindowsHookEx(lngHook)
End Sub