Something like:
OFFSET(G10,5,1,3,4)
but you need to specify in which direction you are counting rows and columns and you need to know if the matrix is 3 high or 4 high by 3 wide or 4 wide.
Also, this function has to be used within another to work..or you will get a #Value error..
e.g. =Sum(OFFSET(G10,5,1,3,4)) will sum the values in your matrix.