How to hide selected item in datagridviewcombobox

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C#

I am using combobox inside my datagridview. It is connected to the database. Once I select an item (items in tblTime) in the combobox at first cell located at first column, the item selected should not anymore be seen in the combobox at the second cell which is also located at the first column. If I select the button inside the datagridview, that is the time that the comboboxes were refresh. Or in short, I just wanted to hide the item selected from the combobox inside my datagridview for the item not to be selected again in the next cells.

Can anyone help me?

void Timeout()
        {
            conn = new SqlConnection(connec.GetServer());
            conn.Open();
            string q = "select Distinct TimeOUT from tblTime Where Temp= '" +"f"+ "'";
            SqlDataAdapter da = new SqlDataAdapter(q, conn);

            DataTable dt = new DataTable();
            da.Fill(dt);
            //Craete combo column

            DataGridViewComboBoxColumn combo2 = new DataGridViewComboBoxColumn();

            //Assing dataSource
            combo2.DataSource = dt;

            //Assing table Field on combo

            combo2.DisplayMember = "TimeOUT";
            combo2.ValueMember = "TimeOUT";
            combo2.HeaderText = "TimeOUT";
           
            //Adding combo box column in dataGridView

            dataGridView1.Columns.Insert(2, combo2); // 0 is the number of array to the field found in the database.
            dataGridView1.Refresh();


         
        }