Get highest value from scales and remove unnecessary words - vb.net

Question

I created a little program to get weight from scales via COM port. But then I turn on program. It's start to loop (creating long list) SV 0 KG in Label. And if weight increase it's also loop, for e.g. SV 0 KG, SV 50 KG, SV 48 KG, SV 0 KG and etc..
So my question is how to stop loop and always show one value?
And second question can I use Replace("SV", " ") or there is other better method?
Dim myPort As Array
Delegate Sub SetTextCallback(ByVal [text] As String)
Private Sub frmMain_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
myPort = IO.Ports.SerialPort.GetPortNames()
cmbBaud.Items.Add(9600)
cmbBaud.Items.Add(19200)
cmbBaud.Items.Add(38400)
cmbBaud.Items.Add(57600)
cmbBaud.Items.Add(115200)
For i = 0 To UBound(myPort)
cmbPort.Items.Add(myPort(i))
Next
cmbPort.Text = cmbPort.Items.Item(0)
cmbBaud.Text = cmbBaud.Items.Item(0)
btnDisconnect.Enabled = False
End Sub
Private Sub btnConnect_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnConnect.Click
SerialPort1.PortName = cmbPort.Text
SerialPort1.BaudRate = cmbBaud.Text
SerialPort1.Parity = IO.Ports.Parity.None
SerialPort1.StopBits = IO.Ports.StopBits.One
SerialPort1.DataBits = 8
SerialPort1.Open()
btnConnect.Enabled = False
btnDisconnect.Enabled = True
End Sub
Private Sub btnDisconnect_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDisconnect.Click
SerialPort1.Close()
btnConnect.Enabled = True
btnDisconnect.Enabled = False
End Sub
Private Sub btnSend_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSend.Click
SerialPort1.Write(txtTransmit.Text & vbCr)
End Sub
Private Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
ReceivedText(SerialPort1.ReadExisting())
End Sub
Private Sub ReceivedText(ByVal [text] As String)
If Me.rtbReceived.InvokeRequired Then
Dim x As New SetTextCallback(AddressOf ReceivedText)
Me.Invoke(x, New Object() {(text)})
Else
Me.rtbReceived.Text &= [text]
End If
End Sub
Private Sub cmbPort_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmbPort.SelectedIndexChanged
If SerialPort1.IsOpen = False Then
SerialPort1.PortName = cmbPort.Text
Else
MsgBox("Valid only if port is Closed", vbCritical)
End If
End Sub
Private Sub cmbBaud_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmbBaud.SelectedIndexChanged
If SerialPort1.IsOpen = False Then
SerialPort1.BaudRate = cmbBaud.Text
Else
MsgBox("Valid only if port is Closed", vbCritical)
End If
End Sub
Private Sub rtbReceived_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles rtbReceived.TextChanged
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDisconnect.Click
rtbReceived.Text = " "
End Sub
Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
SerialPort1.Write(txtTransmit.Text & vbCr)
End Sub