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
&& columnLevelList.size( ) != 0 )
				{
					aggstr = (String) columnLevelList.get( columnLevelList.size( ) - 1 );
				}
				else if ( rowLevelList.size( ) != 0
						&& columnLevelList.size( ) != 0 )
				{
					aggstr = (String) rowLevelList.get( rowLevelList.size( ) - 1 )
							+ ","
							+ (String) columnLevelList.get( columnLevelList.size( ) - 1 );
				}
			}
			else if ( getDataItemContainer( ) instanceof AggregationCellHandle )
			{
				AggregationCellHandle cellHandle = (AggregationCellHandle) getDataItemContainer( );
				if ( cellHandle.getAggregationOnRow( ) != null )
				{
					aggstr += cellHandle.getAggregationOnRow( ).getFullName( );
					if ( cellHandle.getAggregationOnColumn( ) != null )
					{
						aggstr += ","; 
					}
				}
				if ( cellHandle.getAggregationOnColumn( ) != null )
				{
					aggstr += cellHandle.getAggregationOnColumn( )
							.getFullName( );
				}
			}
			else if ( container instanceof AggregationCellHandle )