September 6th, 2007, 7:00 am
Do you want to estimate using the historical volatility or do you want to get to the market levels for the spread options? If you just want an estimate of the spread volatility then, if you have a dollar product (which guess is what you are after) then you could enter USSW2 Index USSW10 Index HS, which presents you with the historical movements of the spread and its analysis, from which you could guestimate the probability you are after. FYI - it is close, if not equal to 0%.