Predicting Sales

Hello All,

I am new here just began my career after leaving college. I work at an ice arena as the concessions manager. I have a theory that given the expected attendance I can relatively predict the quantity of each item I will sell. Unfortunately so far my data set does not correlate a linear trend line, especially for beer. A polynomial trend line on excel is giving me the highest R^2 value. Is it appropriate to use a polynomial regression line for somehting like this. Also, how do I derive the formula for a polynomial regression line if attendance figures are not evenly intervaled excel does not give me a good equation. Hope someone can help me get started in the right direction. Email me if you can help and i can show you my data. It has been very interesting thus far. Thanks! I am on the right track but I am a little has been a few years since advanced stats...