thread synchronization and GUI problem

Hello, I am using Visual Studio 2005 .Net, coding in C#. I am working
through the threading walkthrough:

ms-help://MS.VSCC.v80/MS.MSDNQTR.v80. en/MS.MSDN.v80/MS.VisualStudio .v80.en/dv_fxmclicc/html/7bc03b7b-d680-499b-8179-5f414b2d650c.ht m

and have been able to get that to work as designed. However, I coded up a
slight variant of that example to update the GUI while each thread is running
rather than only at the end of each thread. My experience is that the GUI is
locked up while each thread is running, though. I have a simple Windows App
form with 2 buttons, 2 text boxes, and 2 labels, and then a class called
Loopy (analogous to the walkthrough Calculator class) [attached below]. My
intention is to loop from 1 to N, where N in a number entered in a text box,
and then display the value of the loop variable on the GUI by updating a
label. Each button-textbox-label combo performs a different loop in a
separate thread. Is there a glaring error in the code or do I just have a
conceptual misunderstandin g?

Thanks,
Don
namespace ThreadEventTest
{
public partial class Form1 : Form
{
Loopy Loopy1;
public delegate void LoopWHandler(in t current);
public delegate void LoopCHandler();

public Form1()
{
InitializeCompo nent();
Loopy1 = new Loopy();
Loopy1.Loop1Wor king += new
Loopy.Loop1Work ingHandler(this .Loop1WHandler) ;
Loopy1.Loop2Wor king += new
Loopy.Loop2Work ingHandler(this .Loop2WHandler) ;
Loopy1.Loop1Com plete += new
Loopy.Loop1Comp leteHandler(thi s.Loop1CHandler );
Loopy1.Loop2Com plete += new
Loopy.Loop2Comp leteHandler(thi s.Loop2CHandler );
}

private void button1_Click(o bject sender, EventArgs e)
{
Loopy1.var1 = int.Parse(textB ox1.Text);
// Disables the btnFactorial1 until this calculation is complete.
button1.Enabled = false;
Loopy1.ChooseTh reads(1);
}

private void button2_Click(o bject sender, EventArgs e)
{
Loopy1.var2 = int.Parse(textB ox2.Text);
// Disables the btnFactorial1 until this calculation is complete.
button2.Enabled = false;
Loopy1.ChooseTh reads(2);
}

protected void Loop1WHandler(i nt current)
// Displays the returned value in the appropriate label.
{
this.BeginInvok e(new LoopWHandler(L1 WHandler), new Object[] {
current });
}

protected void Loop2WHandler(i nt current)
{
this.BeginInvok e(new LoopWHandler(L2 WHandler), new Object[] {
current });
}

protected void Loop1CHandler()
// Displays the returned value in the appropriate label.
{
this.BeginInvok e(new LoopCHandler(L1 CHandler), new Object[] {});
}

protected void Loop2CHandler()
{
this.BeginInvok e(new LoopCHandler(L2 CHandler), new Object[] {});
}

public void L1WHandler(int current)
{
label1.Text = current.ToStrin g();
}
public void L2WHandler(int current)
{
label2.Text = current.ToStrin g();
}
public void L1CHandler()
{
button1.Enabled = true;
}
public void L2CHandler()
{
button2.Enabled = true;
}
}
}

namespace ThreadEventTest
{
public partial class Loopy : Component
{
public int var1;
public int current1;
public int var2;
public int current2;

public delegate void Loop1WorkingHan dler(int current);
public delegate void Loop2WorkingHan dler(int current);
public delegate void Loop1CompleteHa ndler();
public delegate void Loop2CompleteHa ndler();

public event Loop1WorkingHan dler Loop1Working;
public event Loop2WorkingHan dler Loop2Working;
public event Loop1CompleteHa ndler Loop1Complete;
public event Loop2CompleteHa ndler Loop2Complete;

public System.Threadin g.Thread Loop1Thread;
public System.Threadin g.Thread Loop2Thread;

public void Loop1()
{
for (int i = 1; i <= var1; i++)
{
lock (this)
{
current1 = i;
}
Loop1Working(cu rrent1);
}
Loop1Complete() ;
}

public void Loop2()
{
for (int i = 1; i <= var2; i++)
{
lock (this)
{
current2 = i;
}
Loop2Working(cu rrent2);
}
Loop2Complete() ;
}

public void ChooseThreads(i nt threadNumber)
{
// Determines which thread to start based on the value it
receives.
switch (threadNumber)
{
case 1:
// Sets the thread using the AddressOf the subroutine
where
// the thread will start.
Loop1Thread = new System.Threadin g.Thread(new
System.Threadin g.ThreadStart(t his.Loop1));
// Starts the thread.
Loop1Thread.Sta rt();
break;
case 2:
Loop2Thread = new
System.Threadin g.Thread(new
System.Threadin g.ThreadStart(t his.Loop2));
Loop2Thread.Sta rt();
break;
}
}

public Loopy()
{
InitializeCompo nent();
}

public Loopy(IContaine r container)
{
container.Add(t his);

InitializeCompo nent();
}
}
}