（仅供参考）
向系统菜单中添加新项，并且执行对应事件，在窗体任意位置弹出系统菜单，并且执行事件
'窗体
Option Explicit
Private Sub Form_Load()
On Error Resume Next
lhSysMenu = GetSystemMenu(hwnd, 0&)
lRet = AppendMenu(lhSysMenu, MF_SEPARATOR, 0&, vbNullString)
lRet = AppendMenu(lhSysMenu, MF_STRING, IDM_ABOUT, "About...")
Show
ProcOld = SetWindowLong(hwnd, GWL_WNDPROC, AddressOf WindowProc)
End Sub
Private Sub Form_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
Dim r As RECT
Dim p As POINTAPI
If Button = vbRightButton Then
GetCursorPos p
TrackPopupMenu lhSysMenu, 0, p.X, p.Y, 0, Me.hwnd, r
End If
End Sub
Private Sub Form_Unload(Cancel As Integer)
SetWindowLong hwnd, GWL_WNDPROC, ProcOld
End Sub
'-------------------------------------------------------------
'模块
Option Explicit
Public Declare Function TrackPopupMenu Lib "user32" (ByVal hMenu As Long, ByVal wFlags As Long, ByVal X As Long, ByVal Y As Long, ByVal nReserved As Long, ByVal hwnd As Long, lprc As RECT) As Long
Public Declare Function GetCursorPos Lib "user32" (lpPoint As POINTAPI) As Long
Public Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Public Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" (ByVal lpPrevWndFunc As Long, ByVal hwnd As Long, ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Public Declare Function AppendMenu Lib "user32" Alias "AppendMenuA" (ByVal hMenu As Long, ByVal wFlags As Long, ByVal wIDNewItem As Long, ByVal lpNewItem As String) As Long
Public Declare Function GetSystemMenu Lib "user32" (ByVal hwnd As Long, ByVal bRevert As Long) As Long
Public Type RECT
Left As Long
Top As Long
Right As Long
Bottom As Long
End Type
Public Type POINTAPI
X As Long
Y As Long
End Type
Public ProcOld As Long
Public Const TPM_LEFTALIGN = &H0&
Public Const WM_SYSCOMMAND = &H112
Public Const MF_SEPARATOR = &H800&
Public Const MF_STRING = &H0&
Public Const GWL_WNDPROC = (-4)
Public Const IDM_ABOUT As Long = 1010
Public Const WM_COMMAND = &H111
Public lhSysMenu As Long, lRet As Long
Public Function WindowProc(ByVal hwnd As Long, ByVal iMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Select Case iMsg
Case WM_SYSCOMMAND
If wParam = IDM_ABOUT Then
MsgBox "VB Web Append to System Menu Example", vbInformation, "About"
Exit Function
End If
Case WM_COMMAND
If wParam = IDM_ABOUT Then
MsgBox "VB Web Append to System Menu Example", vbInformation, "About"
Exit Function
Else
CallWindowProc ProcOld, hwnd, WM_SYSCOMMAND, wParam, lParam
WindowProc = 0
Exit Function
End If
End Select
WindowProc = CallWindowProc(ProcOld, hwnd, iMsg, wParam, lParam)
End Function