How do I figure out how many shares of a stock can I buy for any given amount, without actually buying them?

The answer is by using simple mathematics.

First you need to decide how much of each stock you are going to buy - since not all stocks are priced equally some would be $20, other $400 and some 0.05 cents.

$100,000 over ten stocks... Decide what ratio you will hold of each stock. E.g. 6:3:4:1:9:4:3:7:9:2

So totalling the ratio is 48. Now you can use a combination of the ratios and fractions to find out how much stock you can hold with your $100,000.

I may have left you out on a limb there - but this calculation is uneccessary. Why don't you just buy your stock one by one until you run out of money? :P

OK Lets try the example with 2 stocks and $100K
you want the weighting to be 3:4
so you want
3/7ths of your money to go to 1 stock
4/7ths of your money to go to 1 stock

3/7*100K=$42857.14
4/7*100K=$57142.85

Now say stock ZXC was $5 each and stock ABC was $67

Now you go:
$57142.85/$67=852.88 Stocks
$42857.14/$5=8571.43 Stocks

There you go. Now do the similar calculation with your ten stocks! Haha!

Good Luck!