  Interference between vector mesons electroproduced at different longitudinal
coordinates leads within Glauber approximation to a $Q^2$-dependence of nuclear
effects similar to what is expected to be an onset of color transparency (CT).
We suggest such a mapping of the photon energies and virtualities, which
eliminates the undesirable $Q^2$-variation and allows to measure a net CT
effect. We develop a multichannel evolution equation, which for the first time
incorporates CT and the effects of the coherence length in the exclusive
electroproduction of vector mesons.
