When creating a Calculation you are able to select different types of calculation depending on what you would like to do.
Here are the different types and an explanation of what they do.
Before Save – the value is calculated when one of the dependencies is set or changed. It will calculate on save if the dependencies has been changed, or straight away if you use the "Is Calculate on Change" setting and you change the dependencies. (Console only 7.3-7.5, Console and Web Access 7.6 onwards).
After Read – the value is calculated when it is read from the database and the window is displayed. This should only be used when the result is constantly changeing. For example, when you want to see a countdown to breaching.
Scheduled – the value is calculated periodically as defined in Schedule Manager. This is particularly useful for calculating values that you want to report on at predefined intervals, such as asset depreciation values.
Window Calculation – used to dynamically set whether or not fields on a Web Access window are mandatory, read-only, or hidden, based on values selected elsewhere on the window.