When you define two or more calculations in a form, the order in which they are carried out is the order in which you defined the calculations. In some cases, you may need to modify the calculation order to obtain correct results.
For example, if you wanted to use the result obtained from calculating two form fields to calculate the value of a third form field, the first two form fields must be calculated together first to obtain the correct final results.
Acrobat automatically performs all assigned field calculations when you are creating and testing your form fields. For convenience while you work, you can turn off automatic calculation in the Forms Preferences.