  We consider the inverse problem of determining the time dependent magnetic
field of the Schr\"odinger equation in a bounded open subset of $R^n$, with $n
\geq 1$, from a finite number of Neumann data, when the boundary measurement is
taken on an appropriate open subset of the boundary. We prove the Lispchitz
stability of the magnetic potential in the Coulomb gauge class by $n$ times
changing initial value suitably.
