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
IAggrFunction function = getFunctionByDisplayName( cmbFunction.getText( ) );
				if ( function != null )
				{
					IParameterDefn[] params = function.getParameterDefn( );
					for ( final IParameterDefn param : params )
					{
						if ( param.isDataField( ) )
						{
							Control control = paramsMap.get( param.getName( ) );
							if ( ExpressionButtonUtil.getExpressionButton( control ) != null )
							{
								ExpressionButtonUtil.initExpressionButtonControl( control,
										binding,
										ComputedColumn.EXPRESSION_MEMBER );
							}
							else
							{
								if ( control instanceof Combo )
								{
									( (Combo) control ).setText( binding.getExpression( ) );
								}
								else if ( control instanceof CCombo )
								{
									( (CCombo) control ).setText( binding.getExpression( ) );
								}
								else if ( control instanceof Text )
								{
									( (Text) control ).setText( binding.getExpression( ) );
								}
							}