If you need to access granular data that is mostly likely at the same level as your fact, there is no simple way to do it with SSAS.
I've actually had to do something similar to this and the method I used was to add a custom action that would run a SQL query against the SQL DB to return the rowset based on the dimension attributes.
If this is a must and you have the time to spend on developing it, you need to install ASStoredProcedures
which will allow you to execute stored procedures.
Have the detail data stored on your fact table.
Create a stored procedure on your SQL database with the data that accepts dimension attributes (Customer.Name, Date.Month, Date.Date). Based on these attributed, the stored proc should filter out the Fact data and return the limited data set.
Create an Action in SSAS and use the ExecuteSQL to run the stored proc and pass it the dimension attributes. Setup the action as a Rowset.
If everything is configured correctly, you should be able to run the custom action in excel and get the data set from the stored proc.
The concept works, but I built this at my previous company over a year ago so I no longer have access to any of the code I used so I apologize for any inaccuracies.