Ask HN: Need your help in building a stock buying\selling decision engine

I am trying to get some machine help in letting me decide which stocks to buy or sell. I have developed a simple service that downloads data from yahoo daily and I just loop through data to find signals about which stocks are going higher or lower. I check on price and volume data points. I think this is not enough. I would like to make it more smart. For example using my software i find out which stocks going higher or lower from last n number of days but this does not help me in any decision making as stock going up from last 10 days may go lower for next 14 days also. I would appreciate if you would share your experience with me if you have done similar work in the past. Any concrete help will also be appreciated. Please do not just say - you can do news parsing to find the signal. I guess that is too generic. Thanks again in advance for your help.