Rate of change of beta
If you do not need it for a day or a week or something like that, an easy thing to do to get the beta of a security is to use wolframalpha.  Here is a sample query: BETA for AAPL Calculating beta is an important metric, but it is not a be all end all, as there are ways to hedge the beta of your portfolio. So relying on beta is only useful if it is done in conjunction with something else. A high beta security just means that overall the security acts as the market does with some multiplier effect. For a secure portfolio you want beta as close to zero as possible for capital preservation while trying to find ways to exploit alpha.