Magnetically modulated structures have been predicted to form close to quantum critical points in a number of recent theories, although there are no experimental examples of this in practice. PrPtAl is ferromagnetic at low temperature but undergoes two transitions to incommensurate states between 5 and 6 K prior to becoming paramagnetic above 6K. The incommensurate states both have two simultaneous ordering vectors that are not simple multiples of a fundamental modulation. The proposal is to look for a softening in the dispersion of the low energy crystal field level which may explain these complex orderings. The aim is to determine whether the modulated structures are driven by (i) Fermi surface nesting, (ii) competition between nearest neighbour and next nearest neighbour exchange. or (iii) are a consequence of a nearby quantum critical instability or some other mechanism.