  After a measurement, to observe the relative phases of macroscopically
distinguishable states we have to ``undo'' a quantum measurement. We generalise
an earlier model of Peres from two state to N-state quantum system undergoing
measurement process and discuss the issue of observing relative phases of
different branches. We derive an inequality which is satisfied by the relative
phases of macroscopically distinguishable states and consequently any desired
relative phases can not be observed in interference setups. The principle of
macroscopic complementarity is invoked that might be at ease with the
macroscopic world. We illustrate the idea of limit on phase observability in
Stern-Gerlach measurements and the implications are discussed.
