MDX newbie: How do I filter/except based on an intermediate level which is not unique -

i have dimension itemsales hierarchy of levels site->itemtype->item

itemtype not unique. sites can sell same itemtype. want exclude type totals (such unknown)

this must easy i'm stuck. seems except work far can work out, except requires me enumerate every site

except([itemsales].[sites].[itemtype].members],{[itemsales].[site1].[unknown],[itemsales].[site2].[unknown]})

this doesn't if want aggregate @ sites level.

the examples see filter focus on numerical filters measures. can filter on name of member or whatever call key value gets column?

sorry asking such easy question i'm not getting less confused more read.

not sure best way address problem, can filter() function using .name of members keep [itemtype] not 'unknown' :

filter(    [itemsales].[sites].[itemtype].members,    [itemsales].[sites].currentmember.name <> 'unknown'  )