This expression put in an MDX query works

WITH MEMBER [TipologiaDiDati].[PPP] AS
'([TipologiaDiDati].[CNST]-[TipologiaDiDati].[BDGT] )' , SOLVE_ORDER =
0
MEMBER [TipologiaDiDati].[PPP2] AS
'IIF(
[TipologiaDiDati].[BDGT]>0,[TipologiaDiDati].[PPP]/[TipologiaDiDati].[BDGT],
0)' , SOLVE_ORDER = 1

What about making PPP AND PPP2 calculated members of the dimension
TipologiaDiDati? I can't specify the clause SOLVE_ORDER in the formula field
of the sourcer table and so the result is not correct...
Any suggestion?
Thanks Andrea