Mình đã thử rất nhiều cách và kết quả đều là Fail.
Sau khi check kỹ thì khôngđược phép Unprotect khi share file:
In a shared workbook, you cannot:However, this functionality is available:Create an Excel tableInsert or delete blocks of cellsYou can insert entire rows and columns.Delete worksheetsMerge cells or split merged cellsSort or filter by formattingYou can sort or filter by number, text, or date, apply built-in filters, and filter by using the Search box.Add or change conditional formatsYou can use existing conditional formats as cell values change.Add or change data validationYou can use data validation when you type new values.Create or change charts or PivotChart reportsYou can view existing charts and reports.Insert or change pictures or other objectsYou can view existing pictures and objects.Insert or change hyperlinksYou can use existing hyperlinks.Use drawing toolsYou can view existing drawings and graphics.Assign, change, or remove passwordsYou can use existing passwords.Protect or unprotect worksheets or the workbookYou can use existing protection.Create, change, or view scenariosUse the Text to Columns commandGroup or outline dataYou can use existing outlines.Insert automatic subtotalsYou can view existing subtotals.Create data tablesYou can view existing data tables.Create or change PivotTable reportsYou can view existing reports.Create or apply slicersExisting slicers in a workbook are visible after the workbook is shared, but they cannot be changed for standalone slicers or be reapplied to PivotTable data or Cube functions. Any filtering that was applied for the slicer remains intact, whether the slicer is standalone or is used by PivotTable data or Cube functions in the shared workbook.Create or modify sparklinesExisting sparklines in a workbook are displayed after the workbook is shared and will change to reflect updated data. However, you cannot create new sparklines, change their data source, or modify their properties.Write, record, change, view, or assign macrosYou can run existing macros that don't access unavailable features. You can also record shared workbook operations into a macro stored in another nonshared workbook.Add or change Microsoft Excel 4 dialog sheetsChange or delete array formulasExcel will calculate existing array formulas correctly.Work with XML data, including:Import, refresh, and export XML dataAdd, rename, or delete XML mapsMap cells to XML elementsUse the XML Source task pane, XML toolbar, or XML commands on the Data menuUse a data form to add new dataYou can use a data form to find a record.