How to repeated insert into history by textchanged event problem

Question

Hi guys i have 3 textboxes 1,2,3
textbox1 respresent mobileNo
textbox2 represent email
textbox3 represent roomno
I need to update any textboxes from three based on textchanged event
Suppose i need update room no in textbox3 changed event
room no is 22 i need to changed to 3333 then update in history by insert into statment in textchanged event
it make insert 4 times 
first time 3
second time 33
third time 333
four time 3333
how to prevent repeated insert into changes to history

Answer 1

public void UpdateMobileHistory(string ConnectionString,string SerialNo ,string EmployeeNo, string Mobile,string UserID,string DateEdit)
SqlConnection con = new SqlConnection(ConnectionString);
SqlCommand cmd = new SqlCommand();
cmd.Connection = con;
cmd.CommandType = CommandType.Text;
cmd.CommandText = "insert into  dbo.HistoryEmployee values(@SerialNo,@EmployeeNo ,'Contact Data',@DateEdit,@UserID,@Mobile,null,null)";
cmd.Parameters.Add("@SerialNo", SqlDbType.NVarChar, 20);
cmd.Parameters.Add("@EmployeeNo", SqlDbType.NVarChar ,20);
cmd.Parameters.Add("@Mobile", SqlDbType.NVarChar, 50);
cmd.Parameters.Add("@UserID", SqlDbType.NVarChar ,20);
cmd.Parameters.Add("@DateEdit", SqlDbType.NVarChar ,50);
cmd.Parameters["@SerialNo"].Value = SerialNo;
cmd.Parameters["@EmployeeNo"].Value = EmployeeNo;
cmd.Parameters["@Mobile"].Value = Mobile;
cmd.Parameters["@UserID"].Value = UserID;
cmd.Parameters["@DateEdit"].Value = DateEdit;
con.Open();
cmd.ExecuteNonQuery();
con.Close();
public string MaxHistoryEmployee(string ConnectionString)
SqlConnection con = new SqlConnection(ConnectionString);
SqlCommand cmd = new SqlCommand();
cmd.Connection = con;
cmd.CommandType = CommandType.Text;
cmd.CommandText = "select max(SerialNo)+1 from dbo.HistoryEmployee";
con.Open();
string commit = Convert.ToString(cmd.ExecuteScalar());
con.Close();
return commit;
private void textBox1_TextChanged(object sender, EventArgs e)
FleetManagment.Fleet fleetContact1 = new FleetManagment.Fleet();
string ID = fleetContact1.MaxHistoryEmployee("Data Source=" + value1 + ";Initial Catalog=" + value2 + ";User ID=" + value3 + ";Password=" + value4 + "");
fleetContact1.UpdateMobileHistory("Data Source=" + value1 + ";Initial Catalog=" + value2 + ";User ID=" + value3 + ";Password=" + value4 + "",ID ,textBox4.Text, textBox1.Text,label6.Text,label10.Text);
this is all my code