Hi,
I don't want to disappoint you, but for Parallels to fully support DX 10 on a Mac (any Mac !), the underlying graphics chip has to support DX 10.
There is no chance of a suitable software-only solution, since that would really 'destroy' decent frame-rates.
IMHO no MacBook in the near and not so near future will be capable of DX 10 in conjunction with decent frame-rates.
But I let surprise myself if so.
Sorry
Stefan