How to stop multiple appearance of a widget

[Sarma]

hi all,
I have an application in which when I press a button I should get a find dialog box. Thing is if I press the button again, I shouldnot get one more dialog box. The previous one should appear.
My present code is like this:

CPT::CPT(QWidget *parent):QWidget(parent)
 {
    //some other lines of code
    QPushButton *but=new QPushButton(this);
    QObject::connect(but,SIGNAL(clicked()),this,SLOT(findbox()));
   //remaining program
 }
 void CPT::findbox()
 {
    QWidget  *findstr=new QWidget;
    //other widgets added to it
    findstr->show();
 }

CPT::CPT(QWidget *parent):QWidget(parent)
 {
    //some other lines of code
    QPushButton *but=new QPushButton(this);
    QObject::connect(but,SIGNAL(clicked()),this,SLOT(findbox()));
   //remaining program
 }
 void CPT::findbox()
 {
    QWidget  *findstr=new QWidget;
    //other widgets added to it
    findstr->show();
 }

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So kindly help me in this problem.