We wish to investigate the magnetic structure of a series of magnetic multilayers using a new technique we have successfully implemented called Spin Echo Modulated Small Angle Scattering. This is similar to SESANS and probes micron length scales. However as all the spin manipulations are performed before the sample we can use this for measuring magnetic correlation lengths and also using samples in high magnetic fields. We will investigate the magnetic structure of Fe/Si multilayers used in neutron polarising supermirrors. It is important to understand the in-plane magnetic structure in the magnetisation process for further improvement in the soft magnetic properties. Specifically the length scale of lateral correlations due to the fluctuating orientation of the spins in the layer would lead to a good understanding of the in-plane magnetic structure.