While working on an excel file I've got the following error masage : "Too many format cells". I don't mind see this masage but after saving and trying to reopen I couldn't open the file by given this masage again. After a deep investigaion I realized that the Excel keep in Format -> Style a lot of format styles while working on a file. To be able to open the file all styles should be deleted from this location. If you open a very large file with a lot of formating cells you will find hundreds of styles, beside 7 of them the rest are not necessery. The delete botten allow you to delete only one style each time.
Do you know how can I delete all non necessery styles efficiency?