When you deal with options think BS (Black and Scholes Model). There are many BS calculators available. <img src=http://bradley.bradley.edu/~arr/bsm/images/model.gif>
Try this calculator, and check info on Hoadley's site. <img src=http://www.elitetrader.com/vb/attachment.php?s=&postid=3154229>
Thanks again everyone for the info and thanks baro-san for the calculator, that was really interesting to play with. Happily, my profit target was hit yesterday and I made 30%.