In a recent post on this blog, I wrote about customizing the Ribbon in Excel 2010; and I used the Camera Tool as an example of an item you might add as part of that customization. The Camera Tool can be used to watch in one workbook or worksheet values in another workbook or worksheet.
For my simple example here I will use my calculation of the number of days until the next Super Bowl as the information I want to keep watching. In my AllThingsFootball.xlsx workbook I have placed the date of the big game in cell A1: 2/5/2012 and the formula for the current date in cell B1: =today(). Then I can place the formula to subtract the two: =A1-B1 in cell C1. With the formatting for cell C1 set to Number, I can see the number of days from now to the end of the season. Each day the value in B1 will update to the current date, and the difference will automatically update in cell C1.
Now, I need to get busy and do some work in my workbook called ImportantStuff.xlsx, but I also want to continue monitoring the number of days until the championship game. I can use the Camera Tool to capture a live picture of the calculation and place it in ImportantStuff.xlsx. It creates a link to the original cells.