Yes! And thank you very much in advance for the suggestion to clarify.
What Im looking to do with the above script is to zero out the Transition To Bill "New Bill" field by aggregating/moving it into the "Billed" field by simply adding it to the formula for an updated calculation.
Heres the reasoning: When I want to create a current bill, i like to see (by peeking into the "Billed" field formula) what past billing amounts were to get a rough idea of how to bill the current period.