Something like this
A = randi(9,[6 3 6]);
U = 3:5;
% do it with a loop
M = zeros(size(A,1),size(A,2),numel(U));
for k = 1:length(U)
M(:,:,k) = A(U(k),1,2) * A(:,:,U(k));
end
Alternatively, this can be vectorized like so:
% if you're running R2016b or newer
M2 = permute(A(U,1,2),[3 2 1]).*A(:,:,U);
% show that this is the same as using the loop
immse(M,M2)
% if you're running R2016a or older
M3 = bsxfun(@times,permute(A(U,1,2),[3 2 1]),A(:,:,U));
% show that this is the same as using the loop
immse(M,M3)
