如何监视winforms TextBox.SelectionStart属性的更改？

I have a multiline text box, and I'd like to display the user's current line number and column number in a label below the text box. It looks like I can get the line number and column number using the SelectionStart property, GetLineFromCharIndex method, and GetFirstCharIndexOfCurrentLine method. However, I can't see any event that gets fired every time the selection changes in the text box.I have a multiline text box, and I'd like to di