Creating Class with ^form

I have main window, wich creates many identical forms, and i need to close them all. I want to create Class with method Close and form in it. After that put this into vector, and when i need to close all forms, in cicle i use method close.

First i do this:

class header

#pragma once
#include "InstrumentForm.h"
class SubscribedItem
{
public:
        SubscribedItem();
        ~SubscribedItem();
        void Close();
private:
        InstrumentForm ^x; // Here i have problem
};

then i do this:

#pragma once
#include "InstrumentForm.h"
ref class SubscribedItem
{
public:
        SubscribedItem();
        ~SubscribedItem();
        void Close();
private:
        InstrumentForm ^x; // Here i have problem
};

then i do this:

 #pragma once

using namespace std;

namespace Client //namespase of my application, that includes InstrumentForm
{
    ref class SubscribedItem
    {
    public:
        SubscribedItem();
        ~SubscribedItem();
    private:
        InstrumentForm ^x; //c2143
    };
}

but after that, i have error c2143

And if i add #include "InstrumentForm.h" in last variant, a have errors in InstrumentForm.h

How can i add form into the class without problems?