I am pretty much a beginner at this myself but I have made a similar attempt with my application.

In my example, I only update a single table while viewing two. This way the grid is really only bound to a single business object; the details of the grid and not the extra stuff. For example customers and their transactions, the transactions are the items I want to update.

The business object needs to be set up to allow for querying with both tables; customers and transactions.

public DataSet GetAll()
{
	string Sql = "";

	Sql = "SELECT a.TransactionID, a.TransactionInfo, a.TransactionPrice, b.CustomerName " +
		"FROM Transaction a LEFT OUTER JOIN Customer b " +
		"ON a.CustomerID = b.CustomerID " +
		"ORDER BY 1, 2, 3";

	return this.GetAll(Sql);
}

At the same time the Transaction BusinessObject needs some more initialization statements:

public class Transaction : ABusinessObject
{
	public WaitingFacility()
	{
		this.UpdateSelectStatement = "SELECT * FROM Transaction";
		this.TableName = "Transaction";
		this.PrimaryKey = "TransactionID";
	}

...

Of course this would only allow you to update a single table. This is the best I can supply given my limited knowledge.