Multithreading: Communication from Parent thread to child thread

Question

I have a List of threads normally 3 threads each of the threads reference a webbrowser control that communicates with the parent control to populate a datagridview. What I need to do is when the user clicks the button in a datagridviewButtonCell corresponding data will be sent back to the webbrowser control within the child thread that originally communicated with the main thread. but when I try to do this I receive the following error message

'COM object that has been separated from its underlying RCW cannot be used.'

my problem is that I can not figure out how to reference the relevant webbrowser control. I would appreciate any help that anyone can give me.

The language used is c# winforms
.Net 4.0 targeted

Code sample:

The following code is executed when user click on the Start button in the main thread

private void StartSubmit(object idx)
{

/*

method used by the new thread to initialise a 'myBrowser' inherited from the webbrowser control each submitters object is an a custom Control called 'myBrowser'
which holds detail about the function of the object eg:
 
*/

   //index: is an integer value which represents the threads id

   int index = (int)idx;

   //submitters[index] is an instance of the 'myBrowser' control

    submitters[index] = new myBrowser();

   //threads integer id

    submitters[index]._ThreadNum = index;

   // naming convention used 'browser' +the thread index

    submitters[index].Name = "browser" + index;

   //set list in 'myBrowser' class to hold a copy of the list found in the main thread

    submitters[index]._dirs = dirLists[index];

   // suppress and javascript errors the may occur in the 'myBrowser' control

    submitters[index].ScriptErrorsSuppressed = true;

  //execute eventHandler

    submitters[index].DocumentCompleted += new WebBrowserDocumentCompletedEventHandler(DocumentCompleted);

   //advance to the next un-opened address in datagridview the navigate the that address

   //in the 'myBrowser' control.

    SetNextDir(submitters[index]);

}

private void btnStart_Click(object sender, EventArgs e)
{

      // used to fill list<string> for use in each thread.

      fillDirs();

      //connections is the list<Thread> holding the thread that have been opened
      //1 to 10 maximum

      for (int n = 0; n < (connections.Length); n++)

      {

         //initialise new thread to the StartSubmit method passing parameters

         connections[n] = new Thread(new ParameterizedThreadStart(StartSubmit));

         // naming convention used conn + the threadIndex ie: 'conn1' to 'conn10'

         connections[n].Name = "conn" + n.ToString();

         // due to the webbrowser control needing to be ran in the single
         //apartment state

         connections[n].SetApartmentState(ApartmentState.STA);

         //start thread passing the threadIndex

         connections[n].Start(n);

      }

   }

Once the 'myBrowser' control is fully loaded I am inserting form data into webforms found in webpages loaded via data enter into rows found in the datagridview.  Once a user has entered the relevant details into the different areas in the row the can then
clicking a DataGridViewButtonCell that has tha collects the data entered and then has to be send back to the corresponding 'myBrowser' object that is found on a child thread.

Thank you