  We present a theoretical model for formation of molecules in an optical
lattice well where a resonant coupling of atomic and molecular states is
provided by small oscillations of a magnetic field in the vicinity of a
Feshbach resonance. As opposed to an adiabatic sweep over the full resonance,
this provides a coherent coupling with a frequency that can be tuned to meet
resonance conditions in the system. The effective Rabi frequencies for this
coupling are calculated and simulations show perfect Rabi oscillations. Robust
production of molecules with an adiabatic sweep of the modulation frequency is
demonstrated. For very large oscillation amplitudes, the Rabi oscillations are
distorted but still effective and fast association is possible.
