DynamicTextBox
How to make a text box within a chart object that will automatically change to show the content of a cell in the spreadsheet. Warning: The captions are all in Japanese. Further warning: The captions are in bad Japanese.
The recipe is: Make the chart. Make a text box in the chart. With the text box selected, enter a formula (e.g. "=B2") in the formula bar. (Do not type anything directly into the text box.)