Forecast vs. Trend

Problem: I need to create an accurate function that will forecast / trend stats for the remainder of the year or years to come. I have only two years of stats but still need as accurate of a forecast / trend as possible.

This data will mainly be translated into a graph and will visually represent a forecast / trend for the remainder of the year.

I have attached an example of some numbers which can be used to create a function.

Questions related to the attached example:

1) What function could forecast the rest of 2008 while taking 2007 trends into consideration as well

2) What function could forecast 2009, while taking into consideration the 2007 to 2008 trends.

Any help would be appreciated - I will be quick to respond to any questions,

sjak