time-based point system

[Jay]

I'm writing a game script and the point system will be based upon time.
 The less time there is between event one and event two, the higher
score you'll get for event two.  However, I've got a problem figuring
how to do this.  Here's why.  I don't want the score system to just be
a straight charted system.  Y'know, like if the time is between x and y
then the points you get are z.  I want to mathematically figure out the
pointage.  That's what I can't figure out how to do.  If it were such
that the more time there is, the more points there are, that would be
easy.  I could just multiply the time by something or other.  Or, if
there was a time limit between the two events, that, too, would be easy
because I could subtract the amount of time spent from the possible
amount of time and multiply by something for points.  Neither of these
are the case.  Any suggestions?