resizing of dynamic controls in datagridview

Question

i develop a win form in c#, and i created dynamic textbox and added to a datagridview column.now my problem is when i run the form textbox is placed at correct position, and when i maximize the form textbox is not added to the required column.here is my code

 

private void Former_Transactons_Load(object sender, EventArgs e)

{

TextBox tx1 = new TextBox();

Rectangle rect = dataGridView1.GetCellDisplayRectangle(8, -1, true);

rect.X = rect.Location.X + (rect.Width-22);

rect.Y = 10;

tx1.Size = new Size(20, 21);

//tx1.Anchor = (AnchorStyles.Bottom | AnchorStyles.Right);

tx1.Location = rect.Location;

dataGridView1.Controls.Add(tx1);

}