S-Function in xPc-Target don't work

[gonse]

I made a Simulink model, where i'm using an s-function within.
Under Simulink everything is alright and the function (c++) multiply the both input datas, but after uploading on the
target PC and starting the model there the result is zero.

I'm using the MSVC-Compiler.
Do I have to include the c-file in a special way to the model?

Thanks a lot,
Stefan