Help me create Array in Header file for the program

[karthikrao10]

Hey Guys,
I am kind of new to CPP programming, and I am developing a small application which calculates Daily gain in Future Market based on Settlement Prices.
I need a help in creating an array in following Header file. i.e at float settPrice[days_to_delivery]; //

If this is Not the way to do , can you kindly let me know how can I do that?
Note: I have Der.h , Der.cpp and main.cpp files. pasting the Der.h code here

#include<iostream>
#include<string>
using namespace std;

#ifndef Der_H
#define Der_H
class Der {
public:

  void setTradingDetails();
        //setTradeData()-- picks the Trade Price for Day-1  and Number of Days for Delivery

  void getTradingDetails();
        //getTradeData()-- gets the Trade Price for Day-1  and Number of Days for Delivery

private:
  int days_to_delivery;
  float tradePrice;
  int cSize;
  int cQuantity;
 float settPrice[days_to_delivery]; // I need Help here , create a array for settPrice based on days_to_delivery input given in code

};//end of Class


#endif