how to isolate GPS data into pieces?

[cxiong]

I have the GPS data received as:
$GPRMC,040302.663,A,3939.7,N,10506.6,W,0.27,358.86,200804,,*1A

I want to isolate the GPS sentence into individual piece so I can display it into a textbox in a form with the following:

GPSTime:
Latitude:
Longitude:
Velocity:
Heading:

First thing is I need to detect the incoming text $GPRMC, if the $GPRMC is valid then use the data,

Who can I do that? I try to use the select case but it does not work.

Can anybody help me out?

Here is my code:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        AxMSComm1.PortOpen = True
        Button1.Text = "OPENED"
        
    End Sub
 
    
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim gpsdata As String
        Dim txtFilter As String
        gpsdata = AxMSComm1.Input
        TextBox1.Text = gpsdata
        txtFilter = Mid(gpsdata, 1, 6)
        Select Case (txtFilter)
            Case "$GPRMC"
                TextBox2.Text = Mid(gpsdata, 8, 6)  'GPS Time
                TextBox3.Text = Mid(gpsdata, 21, 4) 'Latitude
                TextBox4.Text = Mid(gpsdata, 30, 4) 'Longitude
                'first, I want to make sure the above 3 boxes 
                'get the right data.
 
                'More data (other 2 boxes)will be implement later on
                'textbox5 - later
                'textbox6 - later
 
        End Select
    End Sub
End Class