SQL Server database backup problem

[Michael Newman]

I am using SQL Server 2014 Express with Visual Basic 2013 (Professional edition)

I can backup a database but have a problem that I cannot solve. If I keep clicking on the button to save the database, it does not add a new file based on the time of saving nor does it overwrite to old file. It keeps appending data to the existing file. The file size just gets bigger and bigger.

Here is my save code:

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

        Try
            Dim connection As String = ("Data Source=Apollo\sqlexpress;Initial Catalog=Calendar;Integrated Security=True")

            Dim conn As New SqlConnection(connection)
            conn.Open()

            Dim cmd As New SqlCommand
            cmd.CommandType = CommandType.Text
            cmd.CommandText = "BACKUP DATABASE Calendar TO DISK='D:\Temp\Calendar.BAK  '"
            cmd.Connection = conn
            cmd.ExecuteNonQuery()

            conn.Close()

            MsgBox("Data saved")

        Catch ex As Exception

            MsgBox(ex.Message)

        End Try

I hope that I have inserted the code correctly. I have not used this site for many years and then under another user name and email address

Can someone help please?