i need to implement a project with visual intimacy between persons,can anyone recommends an algorithm for person's intimacy in phone contact?

intimacy attenuate over time(the intimacy attenuates automatically if you havnt click/dial it for a long time).

Assume in my address book:

Person     Intimacy(0-100%)
   A         40%
   B         80%
   C         10%

A's intimacy needs raise after i call A ,like this

Person     Intimacy(0-100%)
   A         42%
   B         80%
   C         10%

nothing happens after follow 5 days, A,B,C's intimacy need decline,like this

Person     Intimacy(0-100%)
   A         37%
   B         78%
   C         8%

thanks for everyone's answer