sample code:
Workbook workbook = new Workbook();
Worksheet orders = workbook.Worksheets[0];
Worksheet hidden = workbook.Worksheets.Add("hidden");
orders.Name = "orders";
Range range = orders.Cells.CreateRange("A1", "A1");
range.Name = "OPENLEVEL";
orders.Cells["A1"].PutValue("enter 160 here");
string v4 = "=ROUND(0.0078125*ROUNDDOWN(ROUND(MIN(OPENLEVEL,IF(MIN(IF(114.014379923409>OPENLEVEL,OPENLEVEL,#N/A),112.7578125)<114.014379923409,MIN(IF(114.014379923409>OPENLEVEL,OPENLEVEL,#N/A),112.7578125),#N/A))/0.0078125,9),0),9)";
hidden.Cells["A1"].Formula = v4;
workbook.Save("test8.xls");