Rule Calculation Screen.
The calculations are limited to the normal arithmetical operations. But they do a fantastic job for all of us in business systems. A complex operation make the Thinking process very involved and beats the SpApp's objective of keeping it simple.
SpApp thinks the way you think. It gets a documentation of your logic in the SpecGuide. Put in as much of business logic, as you need. However, do ensure that your logic is in the right sequence. Do remember, SpApp is your 'Logic Calculator'. You set the logic & SpApp follows it. Hence, the sequencing of your logic is very vital. For example, you want to arrive at the Net Value of the invoice, you should have calculated the basic values, taxes etc before working at the Net Value. This is simple to understand. However, deploy caution when you change logic.
Specify your calculations as a matter of a running sequence of calculations like the way you use a calculator. Set your calculation result to an element in the profile you are in or onto another profile.