// add a crosstab to the report container
SubItemCrosstab crosstab = new SubItemCrosstab(container.SubItems);

// define the data source for the crosstab
crosstab.SourceTablePath = "Customers.Orders(Customers2Orders).Order_Details(Orders2Order Details)";

// add a row and column grouping
crosstab.Definition.Rows.Groupings.Add("Customers.Country");
crosstab.Definition.Columns.Groupings.Add("Month$(Orders.OrderDate)");
crosstab.Definition.Columns.Groupings.Add("Year$(Orders.OrderDate)");

// change the syle for the group labels
crosstab.Definition.Columns.GroupLabel[0].Font.Bold = "True";