用VB实现NPOI如何将单元格样式数据格式设置为最新

Dim workbook As New NPOI.HSSF.UserModel.HSSFWorkbook()
Using fileStream As New FileStream("path_to_excel_file", FileMode.Open, FileAccess.Read)
    workbook = New NPOI.HSSF.UserModel.HSSFWorkbook(fileStream)
End Using

Dim sheet As NPOI.SS.UserModel.ISheet = workbook.GetSheet("sheet_name")

Dim cellStyle As NPOI.SS.UserModel.ICellStyle = workbook.CreateCellStyle()
cellStyle.DataFormat = workbook.CreateDataFormat().GetFormat("data_format")

Dim cell As NPOI.SS.UserModel.ICell = sheet.GetRow(row_index).GetCell(column_index)
cell.CellStyle = cellStyle

Using fileStream As New FileStream("path_to_excel_file", FileMode.Create, FileAccess.Write)
    workbook.Write(fileStream)
End Using