  Walker's Cancellation theorem for abelian groups tells us that if $A$ is
finitely generated and $G$ and $H$ are such that $A \oplus G \cong A \oplus H$,
then $G \cong H$. Michael Deveau showed that the theorem can be effectivized,
but not uniformly. In this paper, we expand on Deveau's initial analysis to
show that the complexity of uniformly outputting an index of an isomorphism
between $G$ and $H$, given indices for $A$, $G$, $H$, the isomorphism between
$A \oplus G$ and $A \oplus H$, and the rank of $A$, is $\mathbf{0'}$.
