Sales forecast

Hi everybody,

I'm trying to forecast sells for the next 12 months given the sells data for the past 14 months. I found it a challening task, so any help would be much appreciated.

1. What I've done so far is finding the avg monthly sells for the last 14 months and increasing that value with a predefined growth percentage for the different scenarios (base, optimistic and pesimistic) I run. For example, suppose the avg monthly sells are 100 000 and expected sells growth for base case scenario is 15%, this returns 115 000 expected growth on a monthly basis. I've done the same analysis, using the same percentage for COGS, which implies that gross margin would stay constant. But it doesn't. I suspect that avg values are the cause ot it.

2. I tried to use some of MS Excel regression formulas such as FORECAST and LINEST. If I use them I cannot run different scenarios for my project!

3. Probably I should use Monte Carolo simulation?!

Thanks in advance,

kras