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
{
			Label lblAggOn = new Label( composite, SWT.NONE );
			lblAggOn.setText( AGGREGATE_ON );
			gridData = new GridData( );
			gridData.verticalAlignment = GridData.BEGINNING;
			lblAggOn.setLayoutData( gridData );
			cmbAggOn = new Combo( composite, SWT.BORDER | SWT.READ_ONLY );
			gridData = new GridData( GridData.FILL_HORIZONTAL );
			gridData.horizontalSpan = 3;
			cmbAggOn.setLayoutData( gridData );
			cmbAggOn.setVisibleItemCount( 30 );
			cmbAggOn.addSelectionListener( new SelectionAdapter( ) {
				public void widgetSelected( SelectionEvent e )
				{
					modifyDialogContent( );
				}
			} );
		}
	}
	private void createCommonSection( Composite composite )
	{
		new Label( composite, SWT.NONE ).setText( EXPRESSION );
		txtExpression = new Text( composite, SWT.BORDER | SWT.WRAP );
		GridData gd = new GridData( GridData.FILL_HORIZONTAL );
		gd.horizontalSpan = 2;
		gd.heightHint = txtExpression.computeSize( SWT.DEFAULT, SWT.DEFAULT ).y
				- txtExpression.getBorderWidth( )
				* 2;
		txtExpression.setLayoutData( gd );