hello, if i have 2 sets of data, e.g. NG and WTI end of day 2 yrs back. could any1 help me with a trading strategy (in excel) something like if the spread between the 2 assets moves over 1sd upward from the median then sell and vice versa for buying. I have some ideas but are completely clueless how to go about it in excel and set this up thru api. Any help greatly appreciated.