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
DimensionViewHandle viewHandle = getCrosstabReportItemHandle( ).getDimension( dimensionName );
		if ( viewHandle == null )
		{
			return retValue;
		}
		int count = viewHandle.getLevelCount( );
		for ( int i = 0; i < count; i++ )
		{
			LevelViewHandle levelHandle = viewHandle.getLevel( i );
			retValue.add( levelHandle.getCubeLevel( ).getName( ) );
		}
		return retValue;
	}
	private CrosstabReportItemHandle getCrosstabReportItemHandle( )
	{
		try
		{
			return (CrosstabReportItemHandle) ( ( (ExtendedItemHandle) bindingHolder ).getReportItem( ) );
		}
		catch ( ExtendedElementException e )
		{
			return null;
		}
	}
	private Object getArgumentValue( ComputedColumnHandle handle, String name )
	{
		Iterator iter = handle.calculationArgumentsIterator( );
		while ( iter.hasNext( ) )
		{
			CalculationArgumentHandle argument = (CalculationArgumentHandle) iter.next( );