Here's an example of how to use the tool :
First of all, I decided NOT to work with an exact calculation of the number of turns needed for researching a tech, since that wouldn't be practical (map size, contacts, difficulty level, ...). Instead I'm assuming that you have a vague idea of how long it took the AI to research a previous tech.
Let's say you think it took the Americans about 30 turns to researh philosophy, for example.
That's the start, now let's look at the spreadsheet :
column A : the tech
column B : the base cost of the tech, as found in the editor.
columns C through AO : the factors that influence research-priority. Row 2 contains the weight of the factor. Factors and weight were discovered by alexman <insert credit here>.
columns AR through DA : the different civs, starting with a fictuous 'vanilla civ'. This is a civ that has no starting techs and no unique unit. I just added that one if you want to see the influence of these factors on an existing civ's preferences.
Per civilization there are two columns. For instance for Americans :
column AR, row 2 : this is the 'base number of turns' - you need to fill this in. Here's how : remember the example above ? Americans got philosophy in 30 turns. in column B you see the base cost factor of philosophy is 6. This means that the base number of turns is 30/6 = 5.00. Fill this in in AR2.
column AS, row 3 and further : if you want to calculate the probability of this tech, fill in 1, otherwise fill in 0.
column AR, row 3 and further : if column AN contains '1', the probability factor is displayed here.
So basically it's very simple : to stick with the example above, let's say that you want to see whether the Americans will be going for mapmaking or polytheism : open the spreadsheet, calculate the '5.00' as explained above, fill in the '1' for the mapmaking and polytheism rows (AS20 and AS21), et voilà : the magic numbers appear (54.27 for mapmaking and 11.27 for polytheism). 
All feedback welcome !
