By default XLC is set to automatically update any equations as a result of a cell formula change or a name change. This is the best way to work when preparing calculation documents allowing you check cell formulas as you go. However if you work with large datasheets XLC’s automatic functionality will slow you down. So XLC has a switch on its toolbar to turn this functionality off and on (it is called the ‘Auto XLC switch’ ). When switched off XLC will not slow Excel at all and equations will not automatically update (you must use the redraw buttons to equations to do so ). Even if you forget to turn off using the ‘Auto XLC switch’ XLC will switch itself off if an automatic update takes longer than 20 seconds (20 seconds is the default ‘automatic equation maximum dwell time’ and it can be set to any value you choose using the about XLC and settings button ).This video explains how it all works.