Control Break - Help!

[map4]

Hello. I am currently working on an assignment where I am given a data file that contains a list of different student id number's and a set of 3-5 different grades. I am suppose to drop the lowest and highest grade and then calculate the average. I am getting lost on how to set this up. Any help?

this is what I have so far:
#include <iostream>
#include <fstream>
#include <iomanip>

using namespace std;
void main ()

{
ifstream fin;
fin.open("Quizzes.dat");

fout.setf(ios::fixed);
fout.setf(ios::showpoint);
fout.precision(2);


int id,score,max=1,min=1,count=1,total=0;
float average;

fin>> id >> score;
max=score;
min=score;
start=id;

while(!fin.eof())
{if (id=start)
{if (score>max)
max=score;
else if (score<min)
min = score;