  The super massive black hole candidate, Sagittarius A*, exhibits variability
from radio to X-ray wavelengths on time scales that correspond to < 10
Schwarzschild radii. We survey the potential of millimeter-wavelength VLBI to
detect and constrain time variable structures that could give rise to such
variations, focusing on a model in which an orbiting hot spot is embedded in an
accretion disk. Non-imaging algorithms are developed that use interferometric
closure quantities to test for periodicity, and applied to an ensemble of
hot-spot models that sample a range of parameter space. We find that structural
periodicity in a wide range of cases can be detected on most potential VLBI
arrays using modern VLBI instrumentation. Future enhancements of mm/sub-mm VLBI
arrays including phased array processors to aggregate VLBI station collecting
area, increased bandwidth recording, and addition of new VLBI sites all
significantly aid periodicity detection. The methods described herein can be
applied to other models of Sagittarius A*, including jet outflows and
Magneto-Hydrodynamic accretion simulations.
