If I insert a textbox in a chart, How do you manipulate a text box in a Chart? Lets say that I want to change the text of the text box every time I enter new data for the chart, how do you refer to the textbox in code?

I found a previous post with an answer of what I want to do(remove the value legend from a chart line, and only leave the last most recent data point show the value) I was thinking to insert a text box that will be linked to this value in the chart data table. Now when I use this method;
http://www.excelforum.com/showthread...ght=chart+text
and I click on the chart, type “=” and give a reference to the textbox, every think in fine, but when I insert a new row so the chart updates automatically (the chart data source has two empty cells long so when I insert a new cell just below the last data point and enter new values the chart updates by itself) the cell reference chances to the net cell below.
Ex. I click Chart, type “=” and go to the chart data table and highlight cell B41 where value is 22, then in the chart formula appears like datatable!$b$41. Them my problem is that when I insert a new row below row 41 the reference changes to datatable!$b$42.
How can I make it so it will keep the value of b41?