Trying to get the Sum of a Currency held variable

Trying to get the Sum of a Currency held variable

In the function below, I am trying to get the sum of a series of Currency variables (student.p1amt, student.p2amt, etc...)
When I run this, I am getting the concatination of the strings, but not the sum of the numbers. How can I change this to sum the values and store them in the 'amtDue' variable?
Thanks!
Mike


void PaymentsSpace.PaymentsDue()
{
    amtDue = "";
    for each student in Students  [ID != 0]
    {
        info student.First_Name + "  " + student.Last_Name + " " + student.p1rec;
        if (student.p1rec.toString()  !=  "Payment 1 Received")
        {
            amtDue = amtDue + student.p1amt;
        }
        if (student.p2rec.toString()  !=  "Payment 2 Received")
        {
            amtDue = amtDue + student.p2amt;
        }
        if (student.p3rec.toString()  !=  "Payment 3 Received")
        {
            amtDue = amtDue + student.p3amt;
        }
        if (student.p4rec.toString()  !=  "Payment 4 Received")
        {
            amtDue = amtDue + student.p4amt;
        }
        if (student.p5rec.toString()  !=  "Payment 5 Received")
        {
            amtDue = amtDue + student.p5amt;
        }
        if (student.p6rec.toString()  !=  "Payment 6 Received")
        {
            amtDue = amtDue + student.p6amt;
        }
        //info "Amount Due: " + amtDue;
    }
   
     info "Amount Due: " + amtDue;
        }
    // end of foreach
}