The Redmine system allows the members of a project to modify their efforts done for a particular ticket, but we are unable to check if such changes have been done. Therefore I kindly request if the Redmine Database can be modified in a way, such that it has two tables where one table keeps the current value of the effort, while the other table contains the previous effort value and the value that it was changed to (current value), so that we can record if any modifications have been done.