Previous studies have shown there is a correlation between the By component of the interplanetary magnetic field (IMF) and the By component observed either in the magnetotail lobe (Fairfield, 1979) or in the plasma sheet (e.g. Petrokovich, 2011; Cao et al., 2014). This effect has been explained theoretically as a consequence of the open model of the magnetosphere (Cowley, 1981). Studies of the effect of IMF By on several magnetospheric processes (Fear & Milan, 2012a,b; Pitkanen et al., 2013; Grocott & Milan, 2014) have indicated that the By component in the tail should depend more strongly on the recent history of the IMF By than on the simultaneous IMF, though estimates of the timescale vary. We report preliminary results of an investigation into how promptly the IMF By component is transferred into the neutral sheet. To carry out this study, Cluster 3 magnetometer data was used, for the period 2001-2009, alongside solar wind data taken from the OMNI database. Neutral sheet crossings during this interval were identified, and crossings during periods rapid change in the solar wind or the magnetotail were excluded. Starting out with the correlation between instantaneous measurements at the magnetopause and the magnetotail (recently reported by Cao et al., 2014), we investigate what lag time gives the strongest correlation. We discuss how our observations fit with other studies and what they tell us about magnetospheric timescales.