Working with multiple sheets is common when you have a number of departments in a company, a number of divisions, maybe different countries, and data has to be extracted from each of those sheets. Maybe you want the revenues from each sheet. Maybe you want the total sales from each sheet. One way to do this is to sum through the sheet. However, this does have disadvantages, in that the sheets thereafter can't be changed in terms of the row layouts and their column layouts. So instead, integrity checks can be built using the indirect function and the formula text function.