By many interpretations, NM was not permitted in conduit in the 2002 code cycle, but because of a wording error, not because it was intended to be prohibited. It was previously permitted, and is permitted in the 2005 code cycle. So _in general_ you can run NM in conduit.
However, as HotLine1 notes, a conduit _outside_ is considered a _wet_ location. NM is not allowed in _wet_ locations.
One solution to your installation technique is to use _UF_ for the entire run from panel, through the carflex, to the disconnect. UF is rated for wet locations, and may also be used in place of NM.
-Jon
