Controlling When Formulas Are Recalculated
Excel immediately and automatically recalculates all the formulas in a worksheet the moment you make a change to any cell referred to in its formulas. This automatic recalculation mode is fine as long as your spreadsheet is relatively small and your edits to it are few.
Working in this mode can, however, be a real drag (both literally and figuratively) when the worksheet is large and contains lots and lots of formulas: You may be forced to wait quite a few seconds while Excel recalculates every loving formula before you can do anything more after each and every editing change you make.
To avoid this hassle, change the recalculation mode from automatic to manual on the Calculation Options drop-down menu on the Ribbon's Formula tab (Alt+MXM) so that Excel recalculates the formulas in the worksheet only when you specifically tell it to by selecting the Calculate Now or Calculate Sheet command button on the Formulas tab, press F9, or save changes to the workbook.