Calculation on date profile fields

[qpurser]

This might be a tricky one and I am counting on those who are smarter as I am to help me

Scenario:
Our members must attend at least 1 meeting every 12 months to retain membership.
I created 2 custom user fields (field 16 and 19) where we enter the dates from the last 2 meetings they attended. Data is entered like 2012-12-01.

What we need:
First we have to see which field is closest to TODAY (actual date)
Then we have to use that field and calculate how many days are left from TODAY they are still member.
For example TODAY = 2012-09-03 and the last meeting = 2012-08-03
The output should be 365 (days in a year) minus 31 (difference from TODAY and Last Meeting) and should say something like "Your membership will expire in xxx days"

Hope somebody can help me
Thanks