Workbook.Unprotect Method (Object)
Removes protection from the workbook. This method has no effect if the workbook is not protected.
Assembly: Microsoft.Office.Tools.Excel (in Microsoft.Office.Tools.Excel.dll)
The case-sensitive password to use to unprotect the workbook. If the workbook is not protected with a password, this parameter is ignored. If you omit this parameter for a workbook that is protected with a password, the method fails.