Use C++ OpenCV in an android application

Hi,
I developed something using OpenCV in C++. I then exported the functions into a dll file. Whitin the Unity Editor, everything works just fine. But if i build the application on an android phone, it seems that the OpenCV function returns nothing and the code after it is not read.
I have read that it is possible to export c++ code into a library usable by android but with my 32 bit windows I did not manage to do it.
Do you have any ideas on how the things could works ?
Thank you
NC