We propose longitudinal field muSR on a 2D molecular magnetic system which has been suggested to have an unusual B-T phase diagram. Our goal is to probe the transition from low-dimensional disorder to 3D ordered magnetism and investigate the crossover to XY and Kosterlitz-Thouless physics that can occur in 2D systems. The new HiFi spectrometer has opened this fascinating avenue of physics for study using longitudinal field muSR and this proposed experiment is a feasibility test to assess the sensitivity of LF muSR to the phase boundaries and associated fluctuation spectrum of 2D molecular magnetic systems which show nonmonotonic phase diagrams. This is important since conventional experimental methods are often insufficient locate long-range magnetic order in these systems. We will make measurements on Cu(ClO4)(pyz)(gly) which has a nonmonotonic phase diagram within HiFi's range.