You are going to need an animation program.
Go to www.download.com and search for 'gif animator' , see what programs come up. Download one of those. You should be able to figure out how to set the delays/etc and use 2 or so frames.
Remember, the most important part here is size. First you are going to need to keep the icon at 50x50 pixels (the dimensions for ns). Also, file size. Animated icons have to be under 1.94k , if the file size is larger then compress it! or cut down the colors.. Good luck.
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