How do I read excel macro in C#

using (var fs = new FileStream("a.xlsx", FileMode.Open, FileAccess.Read))
{
	wb = new XSSFWorkbook(fs);

	for (int i = 0; i < wb.Count; i++)
	{
		comboBox1.Items.Add(wb.GetSheetAt(i).SheetName);
	}


	}

	// clear grid before filling
	dataGridView1.Rows.Clear();
	dataGridView1.Columns.Clear();

	// get sheet
	sh = (XSSFSheet)wb.GetSheet(comboBox1.SelectedItem.ToString());




	int i = 0;
	while (sh.GetRow(i) != null)
	{
		// add necessary columns
		if (dataGridView1.Columns.Count < sh.GetRow(i).Cells.Count)
		{
			for (int j = 0; j < sh.GetRow(i).Cells.Count; j++)
			{
				dataGridView1.Columns.Add("", "");
			}
		}

		// add row
		dataGridView1.Rows.Add();

		// write row value
		for (int j = 0; j < sh.GetRow(i).Cells.Count; j++)
		{
			var cell = sh.GetRow(i).GetCell(j);

			if (cell != null)
			{
				// TODO: you can add more cell types capability, e. g. formula
				switch (cell.CellType)
				{
					case NPOI.SS.UserModel.CellType.Numeric:
						dataGridView1[j, i].Value = sh.GetRow(i).GetCell(j).NumericCellValue;
						break;
					case NPOI.SS.UserModel.CellType.String:
						dataGridView1[j, i].Value = sh.GetRow(i).GetCell(j).StringCellValue;
						break;
				}
			}
		}

		i++;
	}
}