How To Run A Stored Procedure Asynchronously?

I have a lengthy stored procedure that does archiving that I'd just like to start and let it run, quickly returning control back to the ASP.net web page.  To accomplish this my research shows that I should be passing the "adAsyncExecute" option but all of the examples I've been able to find don't jive with the way I execute stored procedures.  Shown below is the code I'm using.  How would I introduce "adAsyncExecute" ?
 
        public static int DoStoredProcedure(SqlConnection aConn, string procName, params SqlParameter[] theParams)
        {
      int retVal = 0;

            SqlCommand aComm = new SqlCommand(procName, aConn);
            aComm.CommandType = CommandType.StoredProcedure;

            foreach(SqlParameter aParam in theParams)
            {
                aComm.Parameters.Add(aParam);
            }

      SqlParameter returnValue = aComm.Parameters.Add("@ReturnValue", SqlDbType.Int);
      returnValue.Direction = ParameterDirection.ReturnValue;

            try
            {
                aConn.Open();
                aComm.ExecuteNonQuery();

        retVal = (int) returnValue.Value;
            }

            catch(Exception ex)
            {
        Debug.Fail("Error running SQL Query: " + ex.Message, "DBTools.DoStoredProcedure");
                throw;
            }

            finally
            {
                aConn.Close();
            }

      return retVal;
        }