C/C++ :: How To Incorporate Exception Handling Code Into Calculate Mortgage Program

How to incorporate exception handling code into my existing calcMortgage code. While I was researching exception handling, I thought "what would happen with my current code if someone input the principal with a comma in it?". Typically people write two hundred thousand like so.... 200,000. While experimenting with my original code, I remembered reading in my research that someone had done their calcMortgage with the output prompt "DO NOT USE COMMAS". So, when checking to see if my code would run, I did not use commas.

Well, guess what...using a comma in the principal causes an error with a negative numerical output. lol PERFECT!!!! Obviously, the easy thing to do would be to put output instructions in the code telling the user NOT to use commas, but the assignment requires me to use exception handling. The code itself works, but the calculation produces a negative monthly payment.

How would I insert exception handling code into my current code to correct this problem??

#include <iostream>
#include <cstdlib>
#include <cmath>
using namespace std;
struct calcMortgage {
double Principal, numYears, IntRate, monthlyPayments;};
int main(){

[Code]...

would I use a try or a throw??