This has been asked for before. If it were easy to calculate winds aloft automatically, every aviation device on the market would do it. Unfortunately, it's not, and requires the user to manually input a fair bit of data. If you have access to a Garmin 430, you can dial up the wind calculation page and see what it's like.
Also, you only get the answer for the conditions you're flying in right then. If you want to check winds 15 minutes later, you need to check your input data and make updates...it's not a "set it and forget it" kind of operation.