  The Space Interferometry Mission (SIM) is the instrument of choice when it
comes to observing astrometric microlensing events where nearby, usually
high-proper-motion stars (``lenses''), pass in front of more distant stars
(``sources''). Each such encounter produces a deflection in the source's
apparent position that when observed by SIM can lead to a precise mass
determination of the nearby lens star. We search for lens-source encounters
during the 2005-2015 period using Hipparcos, ACT and NLTT to select lenses, and
USNO-A2.0 to search for the corresponding sources, and rank these by the SIM
time required for a 1% mass measurement.
  For Hipparcos and ACT lenses, the lens distance and lens-source impact
parameter are precisely determined so the events are well characterized. We
present 32 candidates beginning with a 61 Cyg A event in 2012 that requires
only a few minutes of SIM time. Proxima Centauri and Barnard's star each
generate several events. For NLTT lenses, the distance is known only to a
factor of 3, and the impact parameter only to 1''. Together, these produce
uncertainties of a factor ~10 in the amount of SIM time required. We present a
list of 146 NLTT candidates and show how single-epoch CCD photometry of the
candidates could reduce the uncertainty in SIM time to a factor of ~1.5.
