In this case there is probably a function that will tell you if a matrix is invertable, but there is a more general solution. You can use try and catch to do what the names suggest: try some code and catch the error.
for i=1:length(A)
try
iv=inv(A(:,:,i));
catch
disp('impossible')
end
end
Or:
try
for i=1:length(A)
iv=inv(A(:,:,i));
end
catch
disp('impossible')
end
