Hi jordi,
Unfortunately, there is no option to do this, either in the free or the premium version. Currently, when you change a status, it just grabs the timestamp and shows this as the time it was changed. At the moment, the only way to change the time of a status update would be directly in the database. That being said, one alternative that would allow you to do something along the same lines (in the premium version), would be to use CSS to hide where it shows the time of the status update and then create your own date/time custom field and use that to set a time for the last update of an order.
