You can use the LsaNtStatusToWinError function to convert the NTSTATUS code to a Windows error code.

        Throw New Win32Exception(LsaNtStatusToWinError(ret))

        Throw New Win32Exception(LsaNtStatusToWinError(ret))

NTSTATUS can be converted to a Windows error using LsaNtStatusToWinError

    internal static extern int LsaNtStatusToWinError(int NTSTATUS);

        throw new Win32Exception(Win32Sec.LsaNtStatusToWinError((int)ret));

        throw new Win32Exception(Win32Sec.LsaNtStatusToWinError((int)ret));

        Throw New Win32Exception(LsaNtStatusToWinError(ret))

        Throw New Win32Exception(LsaNtStatusToWinError(ret))

    internal static extern int LsaNtStatusToWinError(int NTSTATUS);

        throw new Win32Exception(Win32Sec.LsaNtStatusToWinError((int)ret));

        throw new Win32Exception(Win32Sec.LsaNtStatusToWinError((int)ret));

        throw new Win32Exception(Win32Sec.LsaNtStatusToWinError((int)ret));

        throw new Win32Exception(Win32Sec.LsaNtStatusToWinError((int)ret));

        throw new Win32Exception(Win32Sec.LsaNtStatusToWinError((int)ret));

        throw new Win32Exception(Win32Sec.LsaNtStatusToWinError(ret));

static extern uint LsaNtStatusToWinError(uint status);

    Private Declare Function LsaNtStatusToWinError Lib "advapi32.dll" ( _

        aWinErrorCode = LsaNtStatusToWinError( aOpenPolicyResult );

            aWinErrorCode = LsaNtStatusToWinError( aLSAResult );

            UInt32 winErrorCode = LsaNtStatusToWinError(resultPolicy);

            UInt32 winErrorCode = LsaNtStatusToWinError(ntstatus);

            UInt32 winErrorCode = LsaNtStatusToWinError(ntstatus);

        private static extern UInt32 LsaNtStatusToWinError(UInt32 status);

        Throw New Win32Exception(LsaNtStatusToWinError(ret))

        Throw New Win32Exception(LsaNtStatusToWinError(ret))

        Throw New Win32Exception(LsaNtStatusToWinError(ret))

        Throw New Win32Exception(LsaNtStatusToWinError(ret))

    private static extern uint LsaNtStatusToWinError(

        uint winErrorCode = LsaNtStatusToWinError(ntsResult);

        uint winErrorCode = LsaNtStatusToWinError(ntsResult);

        uint winErrorCode = LsaNtStatusToWinError(ntsResult);

        uint winErrorCode = LsaNtStatusToWinError(result);

        uint winErrorCode = LsaNtStatusToWinError(ntsResult);

                public static extern WinErrors LsaNtStatusToWinError(WinStatusCodes status);

                            throw new System.ComponentModel.Win32Exception((int)OSCalls.LsaNtStatusToWinError(status));

                                    throw new System.ComponentModel.Win32Exception((int)OSCalls.LsaNtStatusToWinError(status));

                                    throw new System.ComponentModel.Win32Exception((int)OSCalls.LsaNtStatusToWinError(status));