Allow user to change the default web part styles

I have a web part which uses many SharePoint controls like menu开发者_如何学编程, SPGrid, tool bar etc. I want the user to be able to change the style by specifying an external CSS file.

Can somebody tell me how I can achieve this?

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Here is a web part that allows user to provide a CSS file for overriding the stylesused in the web part. This web part allows you to provide the custom CSS file link in the web part property and it overrides the default out of the box style of tool bar.

http://sharepointexplored.wordpress.com/2009/05/17/how-to-override-sharepoint-styles-for-custom-web-parts/

Hope this helps