Modify functionality of "Update Opportunity Totals"

 Hi all,

We are looking to modify the functionality of the button, "Update Opportunity Totals" in the Opportunities screen.

Can you share some pointers as to where can I find the flow, and modify the same to change the fields included maybe. Also, we want to modify the mathematical calculations.

Actually on the click of "Update Opportunity Totals", value of (NRC+MRC*Term/Months) is calculated from Opportunity Product Revenues field and calculated value is displayed on Order Intake field like that I want to calculate the value of (Current MRC+Remaining Term/Months) and need to display this calculated value in (Expected)Order Outtake field.