  We estimate the rate of gravitational microlensing events of cluster stars
due to black holes (BHs) in the globular cluster NGC 5139 ($\omega Cen$).
Theory and observations both indicate that $\omega Cen$ may contain thousands
of BHs, but their mass spectrum and exact distribution are not well
constrained. In this Letter we show that one may observe microlensing events on
a timescale of years in $\omega Cen$, and such an event sample can be used to
infer the BH distribution. Direct detection of BHs will, in the near future,
play a major role in distinguishing binary BH merger channels. Here we explore
how gravitational microlensing can be used to put constraints on BH populations
in globular clusters.
