In this sort of per field audit situation I'd normally add a field (read only or hidden) and workflow the process execution date your important field changes into that new field.
The workflow would let you determine whether it only gets the date set when the value is changed to 'Won' in this scenario. You can then based your views on this date.
Obviously adding the field relies on your role covering customisation. It doesnt help as an end user really.
If you've found this thread useful, dive deeper into User Group community content by role