A complex Excel 2007 workbook could require multiple sheets. By default, Microsoft provides three sheets on each workbook, but you can add as many as you need.

You can sum cells across multiple sheets in Excel. This article presents steps for Adding single-cell values or Adding values in the range of cells.

Microsoft Excel 2010 provides a formula for calculating the average value from multiple worksheets in a workbook. Before you apply this formula, check that each worksheet is formatted the same way.