We investigate the thermally activated flux motion in structures made of DyBa₂Cu₃O₇ layers separated by an alloy of (Y₁₋ₓPrₓ)Ba₂Cu₃O₇. With x=0.4 we have grown a series of samples containing N layers of DyBa₂Cu₃O₇ (24Å thick, N between 1 and 10) separated by 96Å of (Y0.6Pr0.4)Ba₂Cu₃O₇. For H applied parallel to the c-axis, the activation energy for flux motion U, extracted from the lnϱ versus 1/T curves, increases linearly with N for N<3 and then progressively saturates, demonstrating the coupling of the superconducting layers through the alloy.