Use If statement / conditional to output data to one file or another file C++

New to C++. I have a #define variable (global variable? Not sure what these are called in C++) which I can set to a 1 or a 0. If it is == 1, I want my code to output my data to "File_A.txt". If it == 0, I want my code to output the data to "File_B.txt".

I tried to use an if statement when initializing the output file:

#include <iostream>
#include <iomanip>
#include <fstream>

using namespace std;
#define value 1
...
if (value == 1){
  ofstream fout("File_A.txt");
} else if (value == 0){
  ofstream fout("File_B.txt");
       }

but it seems like doing this makes the code not recognize fout as the output file identifier when I try to close the file fout << endl; and rather it thinks that fout is an undeclared variable... When I try to compile, it returns the classic error error: ‘fout’ was not declared in this scope.

I feel like this should be pretty simple, haha. Let me know if I need to supply more specifics. I tried to keep this brief and straight to the point.

Thanks