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
List aggrList = column.getAggregateOnList( );
					if ( aggrList != null )
					{
						for ( Iterator aggrItr = aggrList.iterator( ); aggrItr.hasNext( ); )
						{
							String baseLevel = (String) aggrItr.next( );
							CrosstabUtil.addHierachyAggregateOn( module,
									binding,
									baseLevel,
									rowLevelNameList,
									columnLevelNameList,
									cache );
						}
					}
					bindingList.add( binding );
				}
			}
			finally
			{
				session.shutdown( );
			}
		}
		return bindingList.toArray( new IBinding[bindingList.size( )] );
	}
	private void setDataFieldExpression( ComputedColumnHandle binding )
	{
		if ( binding.getExpression( ) != null )
		{
			if ( isAggregate( ) )
			{