Can someone explain the array function to me.  And, what is the
difference between trending data using the standard trend function, and
adding an array to the trend?

I have five data points (utilization rates for 2001-2005) that I want to
trend out for  30 years.  I would like to do it annually for the first 15
years, and then in 5 year increments.  

Thanks,
Angie