Syntax Highlighting in a richtext box

[ugagrad]

Hey Everyone,
I am trying to find a way to highlight text in a rich text box. I have it the highlighting works but the richtextbox jumps around when you type on it. Basically, it moves the scroll bar one line per keypress until the text you are typing is at the top of the control.

I am using the following code to highlight

    Private Sub ColorVisibleLines()
        Dim priorSelectStart = Me.RTFBox.SelectionStart
        Dim priorSelectLength = Me.RTFBox.SelectionLength
        Dim firstLine As Integer = FirstVisibleLine()
        Dim lastLine As Integer = LastVisibleLine()
        Dim currentLine As Integer = GetLineFromCharIndex(RTFBox.SelectionStart)
        Dim currChar As Integer = GetCharFromLineIndex(currentLine)
        ' Lock the update
        isLocked = True
        LockWindowUpdate(RTFBox.Handle.ToInt32)
        'make the current line black
        Me.RTFBox.SelectionStart = currChar
        Me.RTFBox.SelectionLength = Me.RTFBox.Lines(currentLine).Length
        Me.RTFBox.SelectionColor = Color.Black
        If firstLine = 0 And lastLine = 0 Then
            Return
        Else
            Dim MyRow As DataRow
            Dim rm As System.Text.RegularExpressions.MatchCollection
            Dim m As System.Text.RegularExpressions.Match
            For Each MyRow In Words.Rows
                '"( |^)1.*2( |$)"
                rm = System.Text.RegularExpressions.Regex.Matches(RTFBox.Text, MyRow("Word"))
                For Each m In rm
                    Dim lineToColor = GetLineFromCharIndex(m.Index)
                    If lineToColor >= firstLine And lineToColor <= lastLine Then
                        RTFBox.SelectionStart = m.Index
                        RTFBox.SelectionLength = m.Length
                        RTFBox.SelectionColor = Color.FromName(MyRow("color"))
                    End If
                Next
            Next
        End If
        ' Restore the selectionstart
        Me.RTFBox.SelectionStart = priorSelectStart
        Me.RTFBox.SelectionLength = 0
        Me.RTFBox.SelectionColor = Color.Black
        Me.RTFBox.SelectionLength = priorSelectLength
        LockWindowUpdate(0)
        isLocked = False
    End Sub

Functions of interest may be
FirstVisibleLine() gets the first line visible in the RichTextBox
LastVisibleLine() gets the Last Line visible
LockWindowUpdate() simply locks the UI while the coloring is happening.

For Each MyRow In Words.Rows

Words is a dataset with two columns "word" and "color".
Word contains the regular expression and color is the color to highlight.

The basic purpose of this is to highlight a set of tokens that pretty much use the mask <*> or [*].

Does anyone have any suggestions as how to solve the jumping around problem?

Thanks in advance