Tak ted to nechápu, ale něco jsem omylem smáznul a začlo to makat... Zde je funkční kód:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.OleDb;
using System.Data;
using System.Web;

namespace Objekt
{
    public class test
    {
        public static string getText()
        {
            /* String sConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0; Data Source=" + Server.MapPath("data.xls") + ";Extended Properties=\"Excel 8.0;HDR=No\"";
            OleDbConnection objConn = new OleDbConnection(sConnectionString); */
            String sConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0; Data Source=" + (HttpContext.Current.Server.MapPath ("data.xls")) + ";Extended Properties=\"Excel 8.0;HDR=No\"";
            OleDbConnection objConn = new OleDbConnection(sConnectionString);

            objConn.Open();

            OleDbCommand objCmdSelect = new OleDbCommand("SELECT * FROM [List1$B2:B2]", objConn);
            object nazev = objCmdSelect.ExecuteScalar();
            return nazev.ToString();

            objConn.Close();
        }
    }
           
}