If you are only looking to do this with in the windows form you could try this:
this.OnMouseClick(new MouseEventArgs(MouseButtons.Left,1,500,500,0));
you will be able to pick up the mouse click in here:
private void Form1_MouseClick(object sender, MouseEventArgs e)
{
Label lbl = new Label();
lbl.Top = e.Y;
lbl.Left = e.X;
lbl.Height = 25;
lbl.Width = 100;
lbl.Text = "You clicked here!.";
this.Controls.Add(lbl);
}