Here's what I use.
FusionPro.Composition.SetBodyPageUsage("NSS_F", Field("Shell_F") == "NSSRD_F" || Field("Shell_F") == "NSS_F" || Field("Shell_F") == "NSSFM_F");
FusionPro.Composition.SetBodyPageUsage("NSS_B", Field("Shell_B") == "NSSRD_B" || Field("Shell_B") == "NSS_B" || Field("Shell_B") == "NSSFM_B");
FusionPro.Composition.SetBodyPageUsage("NSSVP_F", Field("Shell_F") == "NSSVP_F");
FusionPro.Composition.SetBodyPageUsage("NSSVP_B", Field("Shell_B") == "NSSVP_B");