Simulate Multipath Rayleigh Fading Channel for OFDM Simulink

Hi,

Does anyone know how it would be possible to simulate a multipath channel for OFDM in Simulink, whose affect is constant across a whole packet i.e. each OFDM symbol experiences the same fading. I had this working in my design using the Rayleigh Fading block but I came back to it the next day and found that it wasn't behaving in the same way.

many thanks Douglas