QCustomPlot Discussion and Comments

hi guys i have a really big issue ... currently i writing a program that plot the USB passed data ... the mainwindow of the program contain a tab widget which with a button you can add more of that tab which the tab call a widget form class that contain a widget that promoted to qcustomplot. the calling code for that is below ... the class named mainplotting ....

static int num_tabs = 0 ;
    ui->tabWidget->addTab(new mainplotting(),QString("Monitor %1").arg(num_tabs));
    num_tabs += 1 ;
    ui->tabWidget->setCurrentIndex(num_tabs);

in the widget form class i have a pushbutton that when you clicked on that the realtimeplot demo (the example in this site) running and when you again click on it it will stop the plotting (using a simple if statement which pause the realtime slot not the timer itself ) ... i actually excepted that the instances from mainplotting which created by new will be different instances ... but when for example i start on the plotting widget (using that button) the other instaces which taken place in other tabs react to that to ...
can any body help me to isolate these widgets .... ? sorry if the solution is not related to the Qcustomplot class .
tnx in advance ....