Worksheets would not be on your MRU list.
Workbooks would be on that list.
You want to just clear the list except for pinned workbooks?
Count the pinned ones......carefully.
Orb>Excel Options>Advanced>Display>Show this number of recent documents.
Set to the number of pinned workbooks and OK
Just the pinned ones will show............if you counted correctly.
Gord Dibben MS Excel MVP