ACCESS PARAMETER (ssrs) urgent

HI ,
how can i access the different dataset parameter in th SSRS. i have created one dataset and define Bu as a parameter. then i created separate dataset called dataset2 and need to access that BU parameter from dataset2. i cant access it using normal way. ex strtoset(@.Bu)..... ?

dear Friend,

Inside my report, I have a field that is the sum of one field in a dataset and other field in other dataset...:

Code Snippet

=Sum(Fields!NC_FPA_OpFinanc.Value, "DataSet_FPAtribuidos")+Sum(Fields!CM_ENT_ReqFundosPropriosRC.Value, "DataSet_ActivoPonderado")

Helped you?
Regards!

|||i need to access it in my mdx query. is it possible to access like following?
SET [FilteredBUList] AS strtoset(@.BU,"Dataset2")