If you Google the archives:
http://groups.google.com/advanced_group_search?as_ugroup=*excel*
you'll find ways to make text blink. However, be aware that blinking
text is frowned on in most commercial applications, and many, if not
most users find it obnoxious.
Note also that blinking cells in a government application in the US
may be a violation of section 508 of the Rehabilitation Act of 1973
(they can trigger epileptic seizures).