static extern bool SwapMouseButton(bool fSwap);

Declare Function SwapMouseButton Lib "user32" (ByVal fSwap As Boolean) As Boolean

http://windowssdk.msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/winui/windowsuserinterface/userinput/mouseinput/mouseinputreference/mouseinputfunctions/swapmousebutton.asp

        static extern bool SwapMouseButton(bool fSwap);

            SwapMouseButton( true );

    static extern long SwapMouseButton(long bSwap);

        SwapMouseButton(1);

        SwapMouseButton(0);