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
return true;
		}
		else if ( left == null && right != null )
		{
			return right.getExpression( ) == null;
		}
		else if ( left != null && right == null )
		{
			return left.getExpression( ) == null;
		}
		else if ( left.getStringExpression( ) == null
				&& right.getStringExpression( ) == null )
			return true;
		else if ( strEquals( left.getStringExpression( ),
				right.getStringExpression( ) )
				&& strEquals( left.getType( ), right.getType( ) ) )
			return true;
		return false;
	}
	private String getControlValue( Control control )
	{
		if ( control instanceof Text )
		{
			return ( (Text) control ).getText( );
		}
		else if ( control instanceof Combo )
		{
			return ( (Combo) control ).getText( );
		}
		return null;