Jose,
Depending on what the surface molecule is, it may be very difficult to
preserve it during cell dissociation.  As an alternative, you might
consider growing the cells on beads, and running the beads with cells
attached to them.  For a reference, see Sterner JM & Leary JF: Use of
biocarrier beads and flow cytometry for single cell studies of
fibronectin gene regulation..., Cell Biophysics 15:159-171 (1989)
Good Luck,
Stefan
--
Stefan Burde
Los Alamos National Laboratory
LS-5, MS M888
Los Alamos, NM 87545
burde at lanl.gov