pairs

Hi, All,

I have an n by m matrix with each entry between 1 and 15000. I want  
to know
the frequency of each pair in 1:15000 that occur together in rows.  
So for
example, if the matrix is
2 5 1 6
1 7 8 2
3 7 6 2
9 8 5 7
Pair (2,6) (un-ordered) occurs together in rows 1 and 3. I want to  
return
the value 2 for this pair as well as that for all pairs. Is there a  
fast way
to do this avoiding loops? Loops take too long.