If you wanna use Excel anyway then why not using Excel right from the start? If Yahoo close data is sufficient for your needs then load it into Excel spread sheet directly.
I would recommend: Budget no problem: CQG Budget a problem: eSignal Someone else is paying for it: Bloomberg Bloomberg's charting is not nearly as good as CQG or eSignal, but the time & sales data quality for a massive number of products and other studies and tools like the Beta scatter plot and the forward curves, etc. etc. are just tits. If you are not trading intraday, the biggest place to save money would be through ordering up delayed data in lieu of real time data. Also, you want to make sure that your data vendor provides the exchange supported spread product data. It will be more accurate and will not contain the lag errors associated with synthetically plotting spread combinations using individual outright instruments where one or more of the leg products has a lower trading frequency than the other legs in the spread.