here is what I was going for

CREATE MEMBER CURRENTCUBE.[CRED IVR END REASON DIM V].[IVRCALL VC CALLENDREASON].[All].[Out %]

AS

([CRED IVR END REASON DIM V].[IVRCALL VC CALLENDREASON].&[Hung Up]+[CRED IVR END REASON DIM V].[IVRCALL VC CALLENDREASON].&[NULL])

/[CRED IVR END REASON DIM V].[IVRCALL VC CALLENDREASON].[ALL],

FORMAT_STRING = 'Percent',

VISIBLE = 1;