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
private void setTypeSelect( String typeSelect )
	{
		if ( cmbType != null )
		{
			if ( typeSelect != null )
				cmbType.select( getItemIndex( cmbType.getItems( ), typeSelect ) );
			else
				cmbType.select( 0 );
		}
	}
	private int getItemIndex( String[] items, String item )
	{
		for ( int i = 0; i < items.length; i++ )
		{
			if ( items[i].equals( item ) )
				return i;
		}
		return -1;
	}
	private void createAggregateSection( Composite composite )
	{
		new Label( composite, SWT.NONE ).setText( FUNCTION );
		cmbFunction = new Combo( composite, SWT.BORDER | SWT.READ_ONLY );
		GridData gd = new GridData( GridData.FILL_HORIZONTAL );
		gd.horizontalSpan = 3;
		cmbFunction.setLayoutData( gd );
		cmbFunction.setVisibleItemCount( 30 );
		
		cmbFunction.addSelectionListener( new SelectionAdapter( ) {
			public void widgetSelected( SelectionEvent e )