The following SQL statement will calculate a monthly loan payment (principal and interest).

select CalculatedPmt =
  cast(
    LoanAmount
      / (power(1+((NoteRate*.01)/cast(12 as float)),LoanTermMonths)-1)
      * (((NoteRate*.01)/cast(12 as float))
      * power(1+((NoteRate*.01)/cast(12 as float)),LoanTermMonths))
    as decimal(10,2))

http://bennyaustin.wordpress.com/2011/03/01/ssas-dmv-queries-cube-metadata/