Help with applying a function to all possible 2x2 submatrices

Hi all,

I'm working with a large data set (on the order of 300X300) and trying to
apply a function which compares the elements of all possible 2x2
submatrices. There are rc(r-1)(c-1) such submatrices, so obviously the naive
method of looping through the rows and columns is computationally unfeasible
for my data set:

   for(i in 1:(nrow(data)-1)) {
     for(j in (i+1):nrow(data)) {
       for (m in 1:(ncol(data)-1)) {
         for (n in (m+1):ncol(data)) {

I have tried using the outer and apply functions to vectorize the task, but
I can't seem to figure out the best method (or any method, for that matter)
to help with what I'm trying to do.