diff --git a/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook.cs b/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook.cs
index 0336aff..fb906e0 100644
--- a/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook.cs
+++ b/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook.cs
@@ -777,5 +777,26 @@
         }
 
         public String Author { get; set; }
+
+        public Boolean LockStructure { get; set; }
+        public XLWorkbook SetLockStructure(Boolean value) { LockStructure = value; return this; }
+        public Boolean LockWindows { get; set; }
+        public XLWorkbook SetLockWindows(Boolean value) { LockWindows = value; return this; }
+
+        public void Protect()
+        {
+            Protect(true);
+        }
+
+        public void Protect(Boolean lockStructure)
+        {
+            Protect(lockStructure, false);
+        }
+
+        public void Protect(Boolean lockStructure, Boolean lockWindows)
+        {
+            LockStructure = lockStructure;
+            LockWindows = LockWindows;
+        }
     }
 }
\ No newline at end of file
diff --git a/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Load.cs b/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Load.cs
index 2625812..cb93d1e 100644
--- a/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Load.cs
+++ b/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Load.cs
@@ -88,6 +88,15 @@
             var wbProps = dSpreadsheet.WorkbookPart.Workbook.WorkbookProperties;
             Use1904DateSystem = wbProps != null && wbProps.Date1904 != null && wbProps.Date1904.Value;
 
+            var wbProtection = dSpreadsheet.WorkbookPart.Workbook.WorkbookProtection;
+            if (wbProtection != null)
+            {
+                if (wbProtection.LockStructure != null)
+                    LockStructure = wbProtection.LockStructure.Value;
+                if (wbProtection.LockWindows != null)
+                    LockWindows = wbProtection.LockWindows.Value;
+            }
+
             var calculationProperties = dSpreadsheet.WorkbookPart.Workbook.CalculationProperties;
             if (calculationProperties != null)
             {
diff --git a/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Save.cs b/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Save.cs
index edcb957..21072b9 100644
--- a/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Save.cs
+++ b/ClosedXML/ClosedXML/ClosedXML/Excel/XLWorkbook_Save.cs
@@ -433,6 +433,20 @@
 
             #endregion
 
+            if (LockStructure || LockWindows)
+            {
+                if (workbook.WorkbookProtection == null)
+                    workbook.WorkbookProtection = new WorkbookProtection();
+
+                workbook.WorkbookProtection.LockStructure = LockStructure;
+                workbook.WorkbookProtection.LockWindows = LockWindows;
+            }
+            else
+            {
+                workbook.WorkbookProtection = null;
+            }
+            
+
             if (workbook.BookViews == null)
                 workbook.BookViews = new BookViews();
 
diff --git a/ClosedXML/ClosedXML/ClosedXML_Sandbox/Program.cs b/ClosedXML/ClosedXML/ClosedXML_Sandbox/Program.cs
index f28b5dd..f99b0a2 100644
--- a/ClosedXML/ClosedXML/ClosedXML_Sandbox/Program.cs
+++ b/ClosedXML/ClosedXML/ClosedXML_Sandbox/Program.cs
@@ -17,10 +17,7 @@
         {
             var wb = new XLWorkbook();
             var ws = wb.AddWorksheet("Sheet");
-            ws.FirstCell().SetValue(1)
-                .CellBelow().SetFormulaA1("IF(A1>0,Yes,No)") // Invalid
-                .CellBelow().SetFormulaA1("IF(A1>0,\"Yes\",\"No\")") // OK
-                .CellBelow().SetFormulaA1("IF(A1>0,TRUE,FALSE)"); // OK
+            wb.Protect();
             wb.SaveAs(@"c:\temp\saved.xlsx");
             Console.WriteLine("Done");
         }