SqlBulkCopy calculated field

I am working on moving a database from MS Access to sql server. To move the data into the new tables I have decided to write a sync routine as the schema has changed quite significantly and it lets me run testing on programs that run off it and resync whenever I need new test data. Then eventually I will do one last sync and start live on the new sql server version.

Unfortunately I have hit a snag, my method is below for copying from Access to SQLServer

public static void BulkCopyAccessToSQLServer
        (string sql, CommandType commandType, DBConnection sqlServerConnection,
            string destinationTable, DBConnection accessConnection, int timeout)
    {
        using (DataTable dt = new DataTable())
        using (OleDbConnection conn = new OleDbConnection(GetConnection(accessConnection)))
        using (OleDbCommand cmd = new OleDbCommand(sql, conn))
        using (OleDbDataAdapter adapter = new OleDbDataAdapter(cmd))
        {
            cmd.CommandType = commandType;
            cmd.Connection.Open();
            adapter.SelectCommand.CommandTimeout = timeout;
            adapter.Fill(dt);

            using (SqlConnection conn2 = new SqlConnection(GetConnection(sqlServerConnection)))
            using (SqlBulkCopy copy = new SqlBulkCopy(conn2))
            {
                conn2.Open();

                copy.DestinationTableName = destinationTable;
                copy.BatchSize = 1000;
                copy.BulkCopyTimeout = timeout;
                copy.WriteToServer(dt);
                copy.NotifyAfter = 1000;
            }
        }
    }

Basically this queries access for the data using the input sql string this has all the correct field names so I don't need to set columnmappings.

This was working until I reached a table with a calculated field. SQLBulkCopy doesn't seem to know to skip the field and tries to update the column which fails with error "The column 'columnName' cannot be modified because it is either a computed column or is the result of a union operator."

Is there an easy way to make it skip the calculated field?

I am hoping not to have to specify a full column mapping.