Filter expression

[jway]

i am using this expression in a slicer:

item(filter(members([Products].[Organization].[Organization]),
caption(members([Products].[Organization].[Organization])) in (#promptmany('POrg','string', sq($PMOrg{$account.personalInfo.userName}))#)),0)

It is returning the correct level in the hierarchy in the prompt but I need it to start with that level and return the members in the hierarchy below it also.
I'm confused on if I need to use the descendants() or set() function in the default value part of the expression above?  Or am I totally off base? I appreciate the help  :)