Revenue Forecast formula for Excel

Question, I've been asked to project revenue for the upcoming quarter based on the past two years. Orders and revenue are my only metrics to go on. It's been a few years since I had to do my own forecasting. Does anyone have a simple formula for projecting based on this type of data? Ex:

2011 orders $Per rev '11 % growth
Jan 100 $50 $5,000
Feb 50 $52 $2,600 -48%
Mar 150 $53 $7,950 206%
Apr 50 $50 $2,500 -69%


I determined the Cost per unit based on rev/orders. I also determined the growth % and graphed out 2011 and 2012. What I'm having trouble remembering is how to forecast the year ahead with this data. Any help is much appreciated.