[SOLVED]Thread message when all threads finished

[globus25]

Okey I wrote simple code like this->

Thread[] ts=new Thread[10];
 
for(int i=0;i<10;i++)
{
ts[i]=new Thread(function);
ts[i].IsBackground = true;
ts[i].Start();
}

So my threads are doing some work in background... but I need some kind of MessageBox when all threads stops working... I don`t mean .Join() because it blocks the main thread which is form application...

I tried making another function to check background if ThreadState is stopped... but it doesn`t work...

Is there any way to show that MessageBox when all are stoppped(not on button stopped-aborted) ?
and I can`t change to threadpool or tasks....