Stop Null Result producing Less than infinity error

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VB

Hi,

I writing a program to alert if a mail queue exceeds a threshold using an SSH control in VB.NET, however if the result if NULL then it throws an exception and displays cannot that value should be less than infinity.

Can anyone shed any light to help me resolve this as I'm new to VB.Net ?

Thanks

Private Function MonitorMAILSERVER()

        Dim connInfoMAILSERVER As New Renci.SshNet.PasswordConnectionInfo("MAILSERVER", "username", "password")
        Dim sshClientMAILSERVER As New Renci.SshNet.SshClient(connInfoMAILSERVER)
        Dim queueMAILSERVER As Renci.SshNet.SshCommand

        Using sshClientMAILSERVER

            sshClientMAILSERVER.Connect()
            queueMAILSERVER = sshClientMAILSERVER.RunCommand("/usr/sbin/postqueue -p | tail -n1 | awk '{print $5}'")
            txtMAILSERVER.Text = queueMAILSERVER.Result
            sshClientMAILSERVER.Disconnect()

        End Using

        If queueMAILSERVER.Result >= 20 Then

            imgMAILSERVER.Image = Mail_Queue_Monitor.My.Resources.red
        Else

            imgMAILSERVER.Image = Mail_Queue_Monitor.My.Resources.green

        End If

    End Function