We present a measurement of the mass difference between the two B^0
mass eigenstates, Delta m_d, using a flavor method based on correlations of B
meson flavor with the charge of other particles produced in ppbar collisions
at sqrt s = 1.8 TeV/c^2.  Such correlations are expected to arise from b quark
hadronization and from B^** decays.  B mesons are partially reconstructed using
the semileptonic decays B^0 -> l^+D^(*)- X and B^+ -> l^+D-bar^0 X.  We obtain
Delta m_d = 0.471^+0.078_ -0.068(stat) +\- 0.034(syst) \hbar ps^-1, and
measure the efficiency and purity of this flavor tagging method for both
charged and neutral B mesons.