55 chars (see update), not counting the sub subName parts. 
sub a{
eval join'*',1..pop
}

sub f {
a($_[0])/(a($_[1])*a($_[0]-$_[1]))
}

[download]

Update: changed code a bit, down to 53 characters now

The 15 year old, freshman programmer,
Stephen Rawls

In reply to Re: Golf: Selection from sets (Choose) by srawls
in thread Golf: Selection from sets (Choose) by knobunc

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