How to refresh the combobox from one form in another

Hi,
I have a form with combobox. I want to enter a new value in the combobox form another form

In the second form I have:

 private void button1_Click(object sender, EventArgs e)
        {
            OleDbCommand com = new OleDbCommand();

            com.Connection = conn;
            com.CommandText = "Insert into Komin ( Komin) values ( ?)";
            com.Parameters.AddWithValue("@Komin", textBox1.Text);
            try
            {
                conn.Open();
              
                OleDbDataAdapter oleDbAdapter1 = new OleDbDataAdapter(new OleDbCommand("Select * from Komin order by ID asc", conn));

                com.ExecuteNonQuery();

                dataset1.Clear();
                oleDbAdapter1.Fill(dataset1, "Komin");

               }
            finally
            {
                textBox1.Text = "";
                conn.Close();
            }
            button2.Focus();          
        }

so, I enter the new value and I can see it in the access database. But when I close the second form I can't see the inserted value in the combobox, until I close and reopen the form. In the first form I have:

private void button11_Click(object sender, EventArgs e)
        {
            Komintent komintent = new Komintent(this);

            komintent.Show();
        }

to open the second form for entering the new value.

What can I do to refresh the combobox in the first box on clicking the close button in the second form?
Now I have:
 private void button2_Click(object sender, EventArgs e)
        {
            
            dog.Show();           
            this.Close();
        }
but if I put this code, two windows are open for the first form.

Please help me if anybody has an idea.

Thanks in advance