OTL Project Time card: Time processing rules

Summary

OTL Project Time card: Time processing rules

Content

OTL: We are using project time card and would like to create processing/calculation rule such that in case if an individual enters more than 40 hours worked, the rule will normalizes the hours to a 40 hours work week when charging to the project.
For example, If I enter 50 hours in Week
12.5 hours are booked against Project A and 37.5 hours are booked against Project B. When calculation rule is applied on the hours, only 10 hours get charged to Project A and 30 hours get charged to Project B. i.e. hours reported for both projects should get reduced by the same percentage (reduced percentage of the total). Anyone has tried similar rule before? Any clues on how to go about the same? Thanks in advance for your help and expertise.