Finding max and min values for a sinusoidal wave

For an assignment, I have to research the extinction of a pendulum.
Now I have a lot of data and it's easy to find the period of the pendulum. To know the rate of extinction, I have to know the log-function of the maximum and minimum.
In a thread from april 2009 Andy Pope was able to produce a solution. Problem is, I can't open the file (is gives me an error).
Can someone please help me?

tim2011110 was so nice to make an attechment of the file (see post below)