  All experiments observing dilepton pairs (e.g. $e^+e^-$, $\mu^+\mu^-$) must
confront the existence of a combinatoric background caused by the combining of
tracks not arising from the same physics vertex. Some method must be devised to
calculate and remove this background. In this document we describe a particular
event-mixing method relying on many of the unique aspects of the SeaQuest
spectrometer and data. The method described here calculates the combinatoric
background with correct normalization; i.e., there is no need to assign a
floating normalization factor that is then determined in a subsequent fitting
procedure. Numerous tests are applied to demonstrate the reliability of the
method.
