New Post: proctect/lock specific cells

        XLWorkbook workbook = new XLWorkbook();
        IXLWorksheet ixlWorksheet = workbook.AddWorksheet("lock test");

        //set values
        ixlWorksheet.Row(1).Cell(1).SetValue("P1");
        ixlWorksheet.Row(1).Cell(2).SetValue("P2");
        ixlWorksheet.Row(1).Cell(3).SetValue("P3");
        ixlWorksheet.Row(1).Cell(4).SetValue("P4");
        ixlWorksheet.Row(1).Cell(5).SetValue("P5");
        ixlWorksheet.Row(1).Cell(6).SetValue("6"); 
        
        //protect
        ixlWorksheet.SelectedRanges.Add(ixlWorksheet.Range(1, 1, 1, 5));
        ixlWorksheet.Protect().SetSelectLockedCells(true);
        ixlWorksheet.SelectedRanges.Clear();