Dim fci As Integer = rtb.GetFirstCharIndexOfCurrentLine()
 
        Dim li As Integer
        Dim ll As Integer
        Dim lt As Integer
        For Each line In rtb.Lines
            ll = line.Length
            If fci < ll Then Exit For
            li += 1
            fci -= ll
            lt += ll + 1
        Next
 
        rtb.SelectionStart = lt 
        rtb.SelectionLength = ll
        rtb.SelectionColor = Color.Red

Those people who think they know everything are a great annoyance to those of us who do - Isaac Asimov