How can I round significant figures in Excel?
I'm going to guess that you want to enter data and display the number of significant figures from measurements made. You could use the same technique to set how many digits you want to display for a cell where you are performing a calculation.
I have a screencast that covers how to do this. It's available below.
I have another screencast which covers how to use Excel for linear regression analysis. Look under Lesson topic 28 Useful Analysis tips for this video.