如何使用工作日编号创建新日期？

I'm using Date.wday to get the weekday number, but then how can I create a new Date with just that number (without using Date.commercial)? I only need the date to be next week's. For example, if I have 2 (Tuesday), the new date would be whatever date next tuesday is (2009-07-28). Thanks!I'm using Date.wday to get the weekday number,