I'm not sure I understand. If you've entered a date, the datedif function
should work. If you've entered TEXT with the :'s etc, you first need to
convert to true Excel dates:
=DATE(RIGHT(B2,2),MID(B2,4,2),LEFT(B2,2)) would convert the text string to a
date (assuming that you've ALWAYS got two chars each for mm, dd and yy).
So =datedif(DATE(RIGHT(B2,2),MID(B2,4,2),LEFT(B2,2)),today(),"y") would
conver the text and then calculate the years that have elapsed since then.