It is shown that it is possible to inhibit the transfer of magnetization in a chemically exchanging system with several sites in dynamic equilibrium, so that the forward and the backward reaction rates involving two selected species can be studied without being significantly perturbed by other exchange processes. This can be achieved either by selective inversion of the magnetization of the two chosen sites in the course of the reaction interval, or alternatively by inversion of all other sites in the network of exchanging nuclei that one wishes to "decouple" from the selected pair of interest. <IMAGE>