How to create 2 dimension array of textboxes

I am trying to create a 2 dimension array of textboxes. However I am a bit lost with the algorithm
 
private void button1_Click(object sender, EventArgs e)
        {
            int numerovariables = Convert.ToInt32(txtNroVariables.Text);
            int x = 30;
            int y=30;
            for (int i = 1; i <= numerovariables; i++)
            {
                TextBox txt = new TextBox();
                txt.Width = 20;
        ...