Problem in Proxy Creation: interface uses external and internal message definitions

Hi experts,

I'm creating a synchronous scenario in Pi 7.0.

I have create MIOS message interface with:

Input message: an external definition (a XSD scheme)

Output message: a MT message type

Now when I create proxy it raise the error: Interface uses external and internal message definitions.

How to solve this problem?

Note that XSD scheme has thousand of fields...

Thanks

Fabio