The day materialfile data has been loadad to Creo Parametric part, the valueset is merged to parts data. If there will be any changes in material definition, there is no handle to control if parts material should be updated.
Solution would be to carry a last modification date, or/and a Windchill revision in material information. So this stamp could be compared with the corresponding materialfile. Now information could be displayed, if the material should be updated. By the way, to do this the materialfile-name should also be known by parts materialdata.