  We have extended the circuit theory of Andreev conductance [Phys.~Rev.~Lett. {\bf 73}, 1420 (1994)] to diffusive superconducting hybrid structures that contain an Aharonov-Bohm ring. The electrostatic potential distribution in the system is predicted to be flux-dependent with a period of the superconducting flux quantum $\Phi_{0}=h/2e$. When at least one tunnel barrier is present, the conductance of the system oscillates with the same period. 
"Electro-flux" effect in superconducting hybrid Aharonov-Bohm rings