building a DLL

I am writing in C++ a DLL for a program, that is probably written in Fortran. This DLL includes a function, that has several arguments, and some of them are then returned as results. Problem is, that some arguments are one- or two-dimensional array of float or double and I don't know, how to declare function header properly.
For non-dimensional variables, this is easy: I just add the & sign (like int &PrjLen) and the value of the PrjLen variable is returned properly to the main program. But for one- and two-dimensional arrays, this does not work. I tried several combinations (like double &Matrix1[6][6], double &Matrix2[][6], double Matrix3[6][6], double Matrix4[][6], ...), yet none of them worked.
Please help me?

here is how I declare it in header file for a function that can be called by c or c++. I suspect it could be used by fortran too, but don't know for sure.

Code:

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extern "C" __declspec(dllimport) double __cdecl foo(double matrix[][6]);

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