Calculating a mid budget year pay increase without disturbing existing calculation

Hello,

I am by no means an excel expert......everything I know about it I learned from Google. I have run into a particular problem trying to figure out how to track a pay increase without having the existing calculations change. I'll try my best to give an example.....

A payroll specialist updates an excel spreadsheet(SS#1) every two weeks of a company that employees about 600 people. SS#1 contains hourly pay rates for each person in the company, as well as other ancillary information. A second spreadsheet (SS#2) is used to track overtime for the company by an upper level supervisor. SS#2 allows the supervisor to keep tabs on his overtime budget without having the request a report from the financial guy every few days. SS#2 is used for one entire budget year, a "running list" so to speak. SS#2 is also used to generate other information that is pertinent to the supervisor, but unrelated to pay.

The problem is that if SS#1 is updated, and 5 people have received a promotion or pay raise, it throws off the total year tally for overtime in SS#2 because it changes all the existing data, too.

Is there a way to "lock" a calculation in SS#2 after it has calculated, so the if new reference data is placed in SS#1, those older calculations will not change?

Clear as mud?