This might not be the best way to do it, but I played with it and it seems to work. If it's not quite what you were looking for it should at least get you started.
Dim intLineNumber As Integer = RichTextBox1.GetLineFromCharIndex(RichTextBox1.SelectionStart) + 1
Dim intCharIndexOfLine As Integer = RichTextBox1.GetFirstCharIndexOfCurrentLine()
Dim intCharIndex As Integer = RichTextBox1.SelectionStart
Dim intCol As Integer = Math.Abs(intCharIndexOfLine - intCharIndex)