How to insert increment(+1) value in access table

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C#3.5

MS-Access

Hi all,

im creating one application in that application i set sales_count+1 if particular user enter detail then in database sales_count should be 1+1=2 like , this sales_count i set base on TODAY date , now i what i want if Database date and system date match then trigger UPDATE query but if not then throw insert query i written code for UPDATE but i unable to write how can i write sales_count+1 in insert query like if new Date system found then insert query should insert sales_count+1 and current date in sytem

Note: preoblem is i unable to write insert query which is increment sales_count for specific Unique_no with current date , im using MS-ACCESS as database

What I have tried:

this.txtinput.MaxLength = 4;

string connectionString = null;
            connectionString = ConfigurationManager.ConnectionStrings["AccessConnectionString"].ConnectionString;
            con.ConnectionString = connectionString;

string access = "select To_Date from Login";
             cmd = new OleDbCommand(access, con);
              con.Open();
              using (OleDbDataReader read = cmd.ExecuteReader())
              {
                  while (read.Read())
                  {
                      string date2 = read["To_Date"].ToString();
                      if (todaydate == date2)
                      {
                          cmd = new OleDbCommand("update Login set Sales_count= IIF(IsNull(Sales_count), 0, Sales_count) + 1, [To_Date]=Date() where [Unique_No]=@Unique_No", con);
                          cmd.Parameters.AddWithValue("@Unique_No", txtinput.Text);
                          con.Open();
                          int n = cmd.ExecuteNonQuery();

                          if (n == 0)
                          {
                              MessageBox.Show("Invalid Unique No.");

                          }
                          else
                          {
                              this.DialogResult = DialogResult.OK;
                          }

                          con.Close();

                       

                      }
                      else
                      {
                           cmd = new OleDbCommand("IF NOT EXISTS(SELECT 1 FROM Login WHERE Unique_No = @Unique_No) INSERT INTO(Sales_count,To_Date)values(?,Date()) ", con);
                          cmd.Parameters.AddWithValue("@Unique_No", txtinput.Text);
                          con.Open();
                          int n = cmd.ExecuteNonQuery();

                          if (n == 0)
                          {
                              MessageBox.Show("Invalid Unique No.");

                          }
                          else
                          {
                              this.DialogResult = DialogResult.OK;
                          }
                          con.Close();


                      }
                  }
              }
               con.Close();