swDxfMultisheet_e non-operational

Hi

Does anyone know why this doesn't do what it's meant to?

swApp.SetUserPreferenceIntegerValue swDxfMultisheet_e.swDxfActiveSheetOnly, True

Similarly this:

DXFOptionsActiveSheetOnly = swModel.GetUserPreferenceIntegerValue(swDxfMultisheet_e.swDxfActiveSheetOnly)

...doesn't seem to return a result that's related to anything.

I'm currently running SW 2008 SP4.

Thanks

SolidworksApi macros