Combine several matrix with NaNs

I need to combine several matrixes of 500x500 elements that contains NaN. The matrixes must be combined in the way they keep their size but replace NaN by the elements of the other matrix.

I can easily do it for two matrixes: % Cx is a strucutre that I use to store these matrixes. Cx has several matrixes e.g Cx(1).Z Cx(2).Z ...

or=Cx(1).Z; %I want to add the elements to the first matrix (or)
nr=Cx(2).Z;  % this is the second matrix

xn=isnan(or); %I select the NaN's

or(xn)=nr(xn); %I can get now combined elements between Cx(1).Z and Cx(2).Z, it works good until here

%I need to do the same now for all the other matrixes in my structure (Cx),so the combination will be cummulative, I mean use the resulting matrix from merging Cx(1).Z and Cx(2).Z to merge with Cx(3).Z, and then use this output to merge with Cx(4).Z .... and so on

I tough that a loop would be usefull

or=Cx(1).Z; 
xn=isnan(or);

for i=1:numel(Cx)

nr=Cx(i).Z;
or(xn)=nr(xn);

end

but the output or is constantly overwrited and I can get a combination of the matrixes

any suggestion?

thanks in advance