you can do the following:
Change when and how formulas are calculated
By default, Microsoft Excel automatically recalculates formulas when the cells that the formula depends on have changed.
Calculate a worksheet or workbook now
Press F9 Calculates formulas that have changed since the last calculation, and formulas dependent on them, in all open workbooks. If a workbook is set for automatic calculation, you do not need to press F9 for calculation.
Press SHIFT+F9 Calculates formulas that have changed since the last calculation, and formulas dependent on them, in the active worksheet.
Press CTRL+ALT+F9 Calculates all formulas in all open workbooks, regardless of whether they have changed since last time or not.
Press CTRL+SHIFT+ALT+F9 Rechecks dependent formulas, and then calculates all formulas in all open workbooks, regardless of whether they have changed since last time or not.
By default it should be auto recalculating. Has anything else changed?