parallel calculation using a DLL

I have searched, with no success, an example of parallel computation  where a called fundamental function is implemented in a DLL.

I.e. the basic structure to be parallelized is:

DO I=1,N,1

CALL SUB1(ZPARM1(I),ZPARM2(I), ..., OUTVAL1(I))

ENDDO

with SUB1 implemented as a DLL.

Does anybody knows some example ?

Regards