whats wrong with my code?

[BtheMan]

I keep having problems with this code for this problem any help would be greatly appreciated
"The payroll manager at Gerston Blankets wants a program that calculates and displays the gross pay for
each of the company’s employees. It also should calculate and display the total gross pay. The payroll
manager will enter the number of hours the employee worked and his or her pay rate. Employees
working more than 40 hours should receive time and one-half for the hours over 40. Use a void function
to determine an employee’s gross pay. Use a value-returning func-tion to accumulate the total gross
pay. The program should display the total gross pay only after the payroll manager has finished entering
the data for all the employees. Use a sentinel value to end the program."

 #include <iostream>  
#include <iomanip>
#include <cmath>  

using namespace std;

void getGrossPay(double hrsWrk, double payRate, double& grossPay);

int main()
{
	// declare variables  
	double hrsWrk = 0.0;
	double payRate = 0.0;
	double totalGrossPay = 0.0;

	char   sentinel = ' ';

	// prime the loop  
	cout << "Do you have hours to enter? Y/N  (N to stop): ";
	cin >> sentinel;

	while (toupper(sentinel) == 'Y')
	{
		cout << "Enter hours worked:\n";
		cin >> hrsWrk;
		cout << "Enter pay rate:\n";
		cin >> payRate;

		// call function for individual gross pay
		double grossPay = getGrossPay(hrsWrk, payRate);
		totalGrossPay += GetTotalGrossPay(grossPay);


		// Display information  
		cout << fixed << setprecision(2);
		cout << "grossPay:$" << grossPay << endl;
		cout << "Do you have any more hours to enter? (Y/N):" << endl;
		cin >> sentinel;
	}


	cout << "totalGrossPay:$" << totalGrossPay << endl;
}

double getGrossPay(double hrsWrk, double payRate)
{
	// calculates and returns the gross Pay 

	double grossPay = 0.0;

	if (hrsWrk <= 40)
	{
		grossPay = hrsWrk * payRate;
	}
	else
	{
		grossPay = (hrsWrk - 40) * (payRate * 1.5) + (40 * payRate);
	}

	return grossPay;
}

[Ihatov]

First of all, your declaration of getGrossPay() at line 7 and definition at line 45 has different number of arguments. Make up your mind. This decision influences line 30 also.

Second of all, the GetTotalGrossPay function you're using at line 31 doesn't exist.
You need to define it.