Example of how to access Excel from C# scripted rule on SV 4.0 and newer:

SV uses open source NPOI library to work with Excel files, so you can utilize it in your script too.

using System.IO;  
using HP.SV.CSharp;  
using NPOI.SS.UserModel;  
using NPOI.XSSF.UserModel;  
  
namespace HP.SV{  
  public class CSharpRule {  
    private const string ExcelFile = @"d:\sample\excel.xlsx";
    private const string SheetName = "Sheet1";
  
    public static void Execute(HpsvRootObject sv) {  
      WriteRequestToExcel(sv);  
      ReadResponseFromExcel(sv);  
    }  
  
    /// <summary>  
    /// Reads cell A2 from excel and writes its content to a response.  
    /// </summary>  
    private static void ReadResponseFromExcel(HpsvRootObject sv) {  
      // read  
      IWorkbook workbook = ReadWorkbook(ExcelFile);  
  
      // get value  
      ISheet sheet = workbook.GetSheet(SheetName);  
      ICell cell = sheet.GetRow(0).GetCell(1);  
      string content = cell.ToString();  
  
      // write Excel value to response  
      sv.Response.response = content;  
    }  
  
    /// <summary>  
    /// Writes request content to A1  
    /// </summary>  
    private static void WriteRequestToExcel(HpsvRootObject sv) {  
      // read  
      IWorkbook workbook = ReadWorkbook(ExcelFile);  
  
      // modify value in an Excek sheet  
      ISheet sheet = workbook.GetSheet(SheetName);  
      ICell cell = sheet.GetRow(0).GetCell(0);  
      cell.SetCellValue(sv.Request.request);  
  
      // write back to file  
      WriteWorkbook(workbook, ExcelFile);  
    }  
  
    private static IWorkbook ReadWorkbook(string file) {  
      IWorkbook workBook;  
      using (var fs = File.OpenRead(file)) {  
        workBook = new XSSFWorkbook(fs);  
      }  
      return workBook;  
    }  
  
    private static void WriteWorkbook(IWorkbook workbook, string file) {  
      using (var fs = File.Open(file, FileMode.Create)) {  
        workbook.Write(fs);  
      }  
    }  
  
  }  
}