how to keep track of input entries used to compute output for conv2(.)

I am using conv2(.). I needed to keep track of index of input elements which were used to compute a particular output element. I wrote the following piece of code for this purpose. So far it is working fine but it doesnt look like a smart way of doing it. Can anyone suggest some better approach.

%-------------------------------------------------------------------------

INPUT = rand(5,5); [inrow incol] = size(INPUT); INPUTindexmatrix=reshape(1:numel(INPUT),inrow,incol);

Channel = [1 1;1 1]; OUTPUT = conv2(INPUT,Channel,'valid'); [Outrow Outcol] = size(OUTPUT);

OUTPUTindexmatrix=reshape(1:numel(OUTPUT),Outrow,Outcol)

CellArray = cell(length(OUTPUT(:)),1); k=0;

Mask=Channel; Matrix = INPUTindexmatrix

%Sliding window approach

for j=1:size(Matrix,2)-size(Mask,2)+1 for i=1:size(Matrix,1)-size(Mask,1)+1

        k=k+1;
        CellArray{k,1}=Matrix(i:i+size(Mask,1)-1,j:j+size(Mask,2)-1);

        CellArray{k}

    end
end

%-------------------------------------------------------------------------