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
try
		{
			CrosstabReportItemHandle xtabHandle = (CrosstabReportItemHandle) ( (ExtendedItemHandle) getBindingHolder( ) ).getReportItem( );
			String[] aggOns = getAggOns( xtabHandle );
			cmbAggOn.setItems( aggOns );
			String aggstr = ""; 
			if ( getBinding( ) != null )
			{
				List aggOnList = getBinding( ).getAggregateOnList( );
				int i = 0;
				for ( Iterator iterator = aggOnList.iterator( ); iterator.hasNext( ); )
				{
					if ( i > 0 )
						aggstr += ","; 
					String name = (String) iterator.next( );
					aggstr += name;
					i++;
				}
			}
			else if ( isTimePeriod( ) )
			{
				List rowLevelList = getCrosstabViewHandleLevels( xtabHandle,
						ICrosstabConstants.ROW_AXIS_TYPE );
				List columnLevelList = getCrosstabViewHandleLevels( xtabHandle,
						ICrosstabConstants.COLUMN_AXIS_TYPE );
				if ( rowLevelList.size( ) != 0 && columnLevelList.size( ) == 0 )
				{
					aggstr = (String) rowLevelList.get( rowLevelList.size( ) - 1 );
				}
				else if ( rowLevelList.size( ) == 0