Summary

A developer asks:

I have an application in which I'd like to execute a declarative rule at the time a work object is reviewed.  How would I accomplish that?

Suggested Approach

Define a Declare Expression rule to be executed, for the particular purposes you have in mind, upon request rather than upon change.

On the Change Tracking tab, set the Calculated value field to Whenever used.

Caution: A downside to this approach is the performance impact of triggering such computations whenever a work object is merely reviewed. 

Therefore, be judicious in defining the conditions that trigger this processing.