Excel.Style style;

style = Globals.ThisWorkbook.Styles.Add("Style1", Type.Missing);

 style.Font.Name = "Calibri";

style.Font.Size = 11;

style.NumberFormat = "General";

style.Borders[(Excel.XlBordersIndex)Excel.Constants.xlTop].LineStyle = Excel.XlLineStyle.xlContinuous;

style.Borders[(Excel.XlBordersIndex)Excel.Constants.xlBottom].LineStyle = Excel.XlLineStyle.xlContinuous;

style.Borders[(Excel.XlBordersIndex)Excel.Constants.xlLeft].LineStyle = Excel.XlLineStyle.xlContinuous;

style.Borders[(Excel.XlBordersIndex)Excel.Constants.xlRight].LineStyle = Excel.XlLineStyle.xlContinuous;

style.HorizontalAlignment = Excel.XlHAlign.xlHAlignCenter;

style.VerticalAlignment = Excel.XlVAlign.xlVAlignCenter;

Set this style object to Excel Range instance

excelRange.Style = style;