replace sub-matrix values with zeros

Hello, I have a large matrix C, which contains a number of matrices in the format C{i}{j}(k1,k2). The size of the matrix (value of k1 and k2) are different for different i and j values. I would like to set all k1 and k2 values to zero except for a certain i and j values. For example, i=1:7, and j varies from 1 to 128 for different i values. I want to keep the values of i=1, and j=1 and replace all other values to zero. e.g. C{1,1}{1,1}. Please help me to make the loop where i can keep the original size of the matrix but replace the values with zero except the target ones. Related information: I encountered this problem when I am using curvelet. I decomposed the image into different scales and wedges. Now I want to do an inverse curvelet transform of the original image without a particular scale and wedge. I would like to separate and visualize the variations at different scales and wedges. I wonder how I can make the matrix right. thanks a lot in advance. please help