Threads in c++/cli - multithreading

Question

I have a function that "simulates" chess PGN .txt files.
The function looks like this:
PGNFileEinlesen^ pGN = gcnew PGNFileEinlesen(cBoxDateiNamen->Text);
Simulation::DctFigur = dctFigur;
//reset(Reset.Komplett);
// Den Header in die Textbox schreiben
for each(String^ s in pGN->CsvHeader)
{
rTextBoxZuege->AppendText(s + Environment::NewLine);
}
rTextBoxZuege->AppendText(Environment::NewLine);
// Sleep vor erstem Zug
System::Threading::Thread::Sleep(zeitIntervall);
for (int i = 1; i <= pGN->DtcZuege->Count; i++)
{
// Falls Siegesbedingung oder Spiel vorzeitit beendet: (*)
// 1-0 --> weiss gewinnt
// 0-1 --> schwarz gewinnt
// 1/2-1/2 --> Remi
// * --> Partie ist noch nicht beendet
addTextRichTextbox(i, pGN->DtcZuege[i]->Split(' ')[0]);
if (partieBeendet(pGN->DtcZuege[i]->Split(' ')[0]))
{
return;
}
Simulation::Zug(pGN->DtcZuege[i]->Split(' ')[0], Farbe::Weiss);
try
{
simulationsZug();
}
catch (Exception^ e)
{
Console::WriteLine("SimulationsZug() " + e->Message);
}
System::Threading::Thread::Sleep(zeitIntervall);
this->farbeAmZug = farbeAmZugAendern();
addTextRichTextbox(pGN->DtcZuege[i]->Split(' ')[1]);
if (partieBeendet(pGN->DtcZuege[i]->Split(' ')[1]))
{
btnReset->PerformClick();
return;
}
Simulation::Zug(pGN->DtcZuege[i]->Split(' ')[1], Farbe::Schwarz);
try
{
simulationsZug();
}
catch (Exception^ e)
{
Console::WriteLine("SimulationsZug() " + e->Message);
}
System::Threading::Thread::Sleep(zeitIntervall);
this->farbeAmZug = farbeAmZugAendern();
}
btnReset->Enabled = true;
Now, the problem is, that if I start the simulation, the whole GUI is freezing until the function reaches the end of the for loop.
I tried to create a new thread:
threadSimulation = gcnew Thread(gcnew ThreadStart(this, &Schachfeld::test));
threadSimulation->Start();
but I get the error, that my thread is overlapping with the actual thread because I access controls from the original thread.
(and functions too)
Could somebody explain to me what I should do? I didn't find very much by googling.
Thank you!