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
modifyDialogContent( );
			}
		} );
		
		IExpressionProvider filterExpressionProvider = new CrosstabAggregationExpressionProvider( this.bindingHolder,
				this.binding ) {
			protected List getChildrenList( Object parent )
			{
				List children = super.getChildrenList( parent );
				List retValue = new ArrayList( );
				retValue.addAll( children );
				if ( parent instanceof MeasureGroupHandle )
				{
					for ( int i = 0; i < children.size( ); i++ )
					{
						Object obj = children.get( i );
						if ( obj instanceof MeasureHandle
								&& ( (MeasureHandle) obj ).isCalculated( ) )
						{
							retValue.remove( obj );
						}
					}
				}
				return retValue;
			}
		};
		ExpressionButtonUtil.createExpressionButton( composite,
				txtFilter,
				filterExpressionProvider,
				this.bindingHolder );