private void dataGridView1_CellEnter(object sender, DataGridViewCellEventArgs e){
   var indice = e.RowIndex;
   dataGridView1.AllowUserToAddRows = false;

   if (indice > 0 && !dataGridView1.Rows[indice].IsNewRow){
     BeginInvoke(new Action(delegate { dataGridView1.Rows.RemoveAt(indice); }));
     dataGridView1.AllowUserToAddRows = true;
   }
}