__declspec(dllexport) void __stdcall MyVar(const char *file, char** feld) 
{
	MATFile *pmat;
	int ndir;
	pmat = matOpen(file, "r");
	feld = matGetDir(pmat, &ndir);
}

Private Declare Sub MyDLLvar Lib "G:\....\getVariables.dll" Alias "MyVar" _
    (ByRef file As String, ByRef x() As String)
....
Aufruf:
Dim lala(20, 20) As String
Call MyDLLvar("G:\.....\Velaro.mat", lala)