Allow us to use formulas for Standard fields

There are some cases where we need to use a Standard field, but we would prefer to have it be calculated based on other fields of data we have. 

Example: Renewal Centre - there are many OOB fields which require being used as they feed in to a lot of the automations and functionality built in to RC reporting, particularly the Analyze tab. 

Forecast is one of those fields, but we want forecast to use a case statement formula, where it uses an override if present, otherwise uses the value in another field. 

Right now we have this built in to a custom field, and then a rule that copies that value to the Forecast field - this provides a lag between updating numbers in RC and showing the impact in the Analyze tab.