Bug 390669 [Accessibility]Press 'Tab' doesn't focus on the next report item when adding relative period aggregation.
xtab/org.eclipse.birt.report.item.crosstab.ui/src/org/eclipse/birt/report/item/crosstab/internal/ui/dialogs/CrosstabBindingDialogHelper.java
String functionString = getFunctionDisplayName( DataAdapterUtil.adaptModelAggregationType( binding.getAggregateFunction( ) ) );
			int itemIndex = getItemIndex( getFunctionDisplayNames( ),
					functionString );
			cmbFunction.select( itemIndex );
			handleFunctionSelectEvent( );
		}
		catch ( AdapterException e )
		{
			ExceptionUtil.handle( e );
		}
		
		
		for ( Iterator iterator = binding.argumentsIterator( ); iterator.hasNext( ); )
		{
			AggregationArgumentHandle arg = (AggregationArgumentHandle) iterator.next( );
			String argName = DataAdapterUtil.adaptArgumentName( arg.getName( ) );
			if ( paramsMap.containsKey( argName ) )
			{
				if ( arg.getValue( ) != null )
				{
					Control control = paramsMap.get( argName );
					ExpressionButtonUtil.initExpressionButtonControl( control,
							arg,
							AggregationArgument.VALUE_MEMBER );
				}
			}
		}
	}
	private String[] getFunctionDisplayNames( )
	{