每次弹出窗口时，如何处理URL中ID值更改的弹出窗口

I'm working with the WatiN tool. I've a scenario where i need to check a checkbox and click on an ok button in a popup window. i've used AttachtoIE method and used the URL attribute to attach to the popup window. Now the problem is that the URL contains an ID attribute, and its value changes each time the popup appears.. how can I handle this or is there any other method other than AttachtoIE? please give some suggestions.I'm working with the WatiN tool. I've a scenari