Console C++ to full Windows

Alright heres the situation: I have made a console based calculator and I need to move it all into windows program. The following code is what I have so far in Windows code.

// First Windows Program
// This program is intended to display a Windows XP themed interface
// and use some basic Windows program functions

#define STRICT
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <iostream>
#include <string>

int PASCAL WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
LPSTR lpCmdLine, int nCmdShow) {
using namespace std;
MessageBox(NULL, "Would you like to do some math?", "Calculator",
MB_OK|MB_ICONINFORMATION|MB_SETFOREGROUND);

return 0;
}

This is my calculator code:

// Calculator

// Include files below

#include <iostream>
#include <string>
#include <math.h>
#include <cstdlib>
using namespace std;

//Beginning of calulator

int main()
{
//Mathematical operators' corresponding number
//Done = 5;
//Subtraction = 4;
//Addition = 3;
//Multiplication = 2;
//Division = 1;

int answer;

//Answer must be initialized to be used

cout << "What basic mathematical operator shall I perform ?" << endl;
cout << "Please answer with: Division(1), Multiplication(2), Addition(3), Subtraction(4)" << endl;
cout << "Square Root(5), Sine(6), Cosine(7), Tangent(8), Exponetial(9) or End Program(10)" << endl;
cout << "Want a operator not seen here? More operators can be added at your request!" << endl;
cin >> answer;

while(answer!=10) // This begins a loop that will only end when answer is equal to 10
{

if (answer == 1) //Division section of the calculator
{
// Long double is the type of variable that can have up to 15 digits
// Again variables must be initialized before using them.
// However because of the braces around this section the variables
// are local and can be initialized/used in other sections again

long double value1;
long double value2;

// This asks for values and then inputs the values into the variables

cout << "Input value to be divided: ";
cin >> value1;
cout << "Input the dividend: ";
cin >> value2;

//Dividing the values and storing the answer to value1

value1 /= value2;
cout << "Answer: "<< value1 << endl <<endl;
cout << "Please input the next operation number you would like to preform." << endl;
cin >> answer;

}

if (answer == 2) //Multiplication section of the calculator
{

long double value1;
long double value2;

cout << "Input first number: ";
cin >> value1;
cout << "Input the second number: ";
cin >> value2;

value1*=value2;
cout << "Answer: "<< value1 << endl <<endl;
cout << "Please input the next operation number you would like to preform." << endl;
cin >> answer;
}
if (answer == 3) //Addition section of the calculator
{

long double value1;
long double value2;

cout << "Input the first number : ";
cin >> value1;
cout << "Input the second number: ";
cin >> value2;

value1+=value2;
cout << "Answer: "<< value1 << endl <<endl;
cout << "Please input the next operation number you would like to preform." << endl;
cin >> answer;
}
if (answer == 4) //Subtraction section of the calculator
{

long double value1;
long double value2;

cout << "Input value to be subtracted from: ";
cin >> value1;
cout << "Input the number to subtract from the first: ";
cin >> value2;

value1-=value2;
cout << "Answer: "<< value1 << endl <<endl;
cout << "Please input the next operation number you would like to preform." << endl;
cin >> answer;
}
if (answer == 5) //root section of the calculator
{

long double value1;
long double value2;

cout << "Input value to be square rooted: ";
cin >> value1;

value2 = sqrt (value1);
cout << "Answer: "<< value2 << endl <<endl;
cout << "Please input the next operation number you would like to preform." << endl;
cin >> answer;
}
if (answer == 6) //sine section of the calculator
{

long double value1;
long double value2;

cout << "Input value to get the sine for: ";
cin >> value1;

value2 = sin (value1);
cout << "Answer: "<< value2 << endl <<endl;
cout << "Please input the next operation number you would like to preform." << endl;
cin >> answer;
}
if (answer == 7) //cosine section of the calculator
{

long double value1;
long double value2;

cout << "Input value to get the cosine for: ";
cin >> value1;

value2 = cos (value1);
cout << "Answer: "<< value2 << endl <<endl;
cout << "Please input the next operation number you would like to preform." << endl;
cin >> answer;
}
if (answer == 8) //tangent section of the calculator
{

long double value1;
long double value2;

cout << "Input value to get the tangent for: ";
cin >> value1;

value2 = tan (value1);
cout << "Answer: " << value2 << endl <<endl;
cout << "Please input the next operation number you would like to preform." << endl;
cin >> answer;
}
if (answer == 9) //exponetial section of the calculator
{

long double value1;
long double value2;

cout << "Input value to raise exponentially: ";
cin >> value1;
cout << "Input exponet: ";
cin >> value2;

cout << "Answer: "<< pow (value1,value2)<< endl <<endl;
cout << "Please input the next operation number you would like to preform." << endl;
cin >> answer;
}
else
{
cout << "Please input a correct number" << endl;
cin >> answer;
}
// Braces are needed at each level of abstraction
}
// Return value shows that program executed as expected and then ends the program
return 0;
}

Thank you for all the help!