C++ :: Calling Subroutines Within DLL

I am using a dll written in FORTRAN to do some calculations and here is how I have set up the program. I have created following files:

C++ source files:
main.cpp
File1.cpp
Header Files:
Datamain.h
DataFile1.h

[Code]....

Here are my questions:

1) I actually want to call Sub2dll from the main program. But the above program does not build and it gives me the following error: In function 'int main()': Sub2dll was not declared in this scope.

When I build this program with the call to Sub2dll in main commented out and instead put that call in File1::Setup function things build well and runs giving the answer expected. How can I make the call to Sub2dll from main.

2) I am including "Datamain.h" in main. However when I build it with out the declaration int Datamain::Index; in main, it gives me the following error: undefined reference to Datamain::Index When I add that declaration to main the error disappears.

I am usiing Code::blocks with MinGW compiler. I have not put the argument list for the subroutine calls since there were not errors in that part.