I was wondering, is there a way to calculate (even an estimation will do) the theoretical change in price of a put option between two past date, given the underlying price, the number of days passed (and number of days to exp' of course), the strike price and everything but volatility and initial prices? I'm working on a spreadsheet where i'm trying to simulate the P/L of writing a put option on a given date then buying to cover a few days after; but I don't have the actual prices of the options nor the volatility, only the change in the price of the underlying asset. would that be possible? my guess is not due to the lack of volatility input. thanks in advance

If you have the starting option price, you can back out the implied volatility from the option price (given you know the underyling's price when you traded the option). black scholes will give you all of the answers you need. google around for an excel implementation. it's pretty simple -- can take a few cells, no programming background required.

You can simulate Black Scholes valuation in excel. Google "black scholes in excel" and you'd find a ton of them. deriving expected realized vol: If you're lazy, you can use the values off NYU Vlab, http://vlab.stern.nyu.edu/ Or you can do it yourself, here's a crude example in excel, http://matdays.blogspot.com/2012/11/excel-data-analysis-33-volatility.html good luck.

To answer the specific answer you asked: no, you can't. You don't have option pricing or volatility, which is really two ways of saying the same thing. If you want option pricing or volatility, there are various vendors out there. ivolatility is one easy one to start with.

You could also download VIX index data and kind of estimate volatility but it will be shoddy work, and almost useless if you're looking at non-ETFs. Backtesting options requires a lot of data and precision is even more important than with other types of contracts.