Add Duration field to sort criteria programatically?

Can someone please tell me how 开发者_如何学编程to add duration(CCK field) to sort criteria of views programmatically because it is not listed there by default?

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If no handler/field is provided in Views you have to refer to the API and write the views plugins to enable what you want to sort by.

http://views2.logrus.com/doc/html/index.html

http://drupal.org/node/235062