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
createExpressionButton( composite, txtExpression );
		txtExpression.addModifyListener( new ModifyListener( ) {
			public void modifyText( ModifyEvent e )
			{
				modifyDialogContent( );
				validate( );
			}
		} );
	}
	private void createMessageSection( Composite composite )
	{
		messageLine = new CLabel( composite, SWT.LEFT );
		GridData layoutData = new GridData( GridData.FILL_HORIZONTAL );
		layoutData.horizontalSpan = 4;
		messageLine.setLayoutData( layoutData );
	}
	protected void handleFunctionSelectEvent( )
	{
		Control[] children = paramsComposite.getChildren( );
		for ( int i = 0; i < children.length; i++ )
		{
			children[i].dispose( );
		}
		IAggrFunction function = getFunctionByDisplayName( cmbFunction.getText( ) );
		if ( function != null )
		{
			paramsMap.clear( );
			IParameterDefn[] params = function.getParameterDefn( );
			if ( params.length > 0 )
			{