It's possible with VBA.
However, note that blinking text is a violation of Section 508 (29
U.S.C. 794d) for government sites in the US, as certain blink rates can
cause seizures in epileptics.
Post by Mike H from similar topic:
Hi,
Fortunately Excel doesn't have an inbuilt function to achieve this. I say
fortunately because in the view of many; including myself, it would be an
irritating distraction that would make me immediatly close the workbook.
Having got that off my chest and if you must do this then look here
http://www.cpearson.com/excel/BlinkingText.aspx
Mike