Check FOCUS-status on Multiple Windows(sub-forms)

[2lights]

Good Day,

I have created a mainWindow with a button to create a new sub-form.
This sub-form can be created multiple times depending on how many times the push button was clicked.
and each sub-form loads a user specified image.

#include <QMainWindow>
#include "miniFormClass.h"
 
namespace Ui {
    class MainWindow;
}
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
 
public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
 
private:
    Ui::MainWindow *ui;
    miniFormClass* msWindow;
...

#include <QMainWindow>
#include "miniFormClass.h"

namespace Ui {
    class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private:
    Ui::MainWindow *ui;
    miniFormClass* msWindow;
...

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and

//On Push Button clicked
    msWindow = new miniFormClass(this);
    msWindow->show();
    msWindow->callDialogUploadImage();

//On Push Button clicked
    msWindow = new miniFormClass(this);
    msWindow->show();
    msWindow->callDialogUploadImage();

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My Problem:
I need a way of keeping track which sub-form has focus, and I need to access certain member variables from that sub-form only, ignoring the other sub-forms until the user changes focus to another sub-form

Whats the way forward...
Thanks in advance