MouseEnter Event Handler for RichTextBox

I'd like to add a MouseEnter event handler to my RichTextBox which I have in a tabcontrol. The following code gets the currently selected RichTextBox:

 private RichTextBox GetRichTextBox()
    {
        RichTextBox rtb = null;
        TabPage tp = tabControl1.SelectedTab;

        if (tp != null)
        {
            rtb = tp.Controls[0] as RichTextBox;
        }

        return rtb;
    }

The next code is what I use to create the new tab with the RichTextBox:

TabPage tp = new TabPage("New Document");
        RichTextBox rtb = new RichTextBox();
        rtb.Dock = DockStyle.Fill;

        tp.Controls.Add(rtb);
        tabControl1.TabPages.Add(tp);

I am not sure how to go about creating the Mouse Enter Event Handler for the RichTextBox that is created. Any help with this would be greatly appreciated.