RichTextBox Selection Problem

I'm parsing through long strings to change the color of certain words in a RichTextBox with this code:

Code:

---

If m_rtbDescription.Find(strStringToHighlight) <> -1 Then
    m_rtbDescription.Select(m_rtbDescription.Find(strStringToHighlight), strStringToHighlight.Length)
    m_rtbDescription.SelectionColor = color.Red
End If

---

This works fine in every instance EXCEPT when the starting index of the selection happens to be 0; then not only does the string I was attempting to highlight become red, but the entire long string does - it doesn't matter what length I put in for .Find's second parameter.

Any ideas what's happening?

Thanks as always,
neef