C++ :: Label Text In For Loop?

I'm trying to print numbers in a label but I'm not having success. For example, I have the following code:

private: System::Void txtLeftWheel_Click_1(System::Object^ sender, System::EventArgs^ e)
{
for (int i = 1; i <= 1000; i++)
{
Sleep(100);
this->lblLeftWheel->Text = (Int32::Parse(this->lblLeftWheel->Text) + i).ToString();
}
}

The idea is that when I click the button, the numbers on the label increment from 1 to 1000.

The Sleep() is there to slow down the loop and the user can see something happening. However, if I put the Sleep() before the label->, the form freezes completely. If I put the Sleep() after the label-> text, the form freezes for a few seconds and the label text goes from 1 and jumps straight to 1000.

The expected functionality is that the label displays numbers 1 through 1000 but increment every second.