请问红色部分代码是什么意思

如题：
红色部分代码是什么运算，其他的消息怎么运算呢？
Public Function CallBackHookProc(ByVal nCode As Long, _
    ByVal wParam As Long, _
    ByVal lParam As Long) As Long
   
    If nCode = HC_ACTION Then
        Dim Msg As CWPSTRUCT
        Call CopyMemory(Msg, ByVal lParam, Len(Msg))
        If Msg.message = WM_COMMAND Then
            If (Msg.wParam And &HFFFF0000) / &H10000 = EN_CHANGE Then
                Debug.Print "GOTCHA"
            End If
        End If
    End If
   
    CallBackHookProc = CallNextHookEx(hHook, nCode, wParam, lParam)
End Function