how to set password expire alert messge for user within before 3 days..?

<pre> Private Sub CheckLastPasswordChangedDate()
        Try
            Con = New SqlConnection(connectionstringhere)
            Con.Open()
            cmd = Con.CreateCommand()
            cmd.CommandText = "SELECT PasswordLastChangedDate FROM YOURTABLENAME WHERE User_ID = '" & txt_Username.Text & "' and Password='" & EncryptData(txt_Password.Text) & "'"
            rdr = cmd.ExecuteReader()
            If rdr.Read Then
                Label1.Text = rdr.GetValue(0).ToString
                If Convert.ToDateTime(rdr.GetValue(0)).AddDays(passwordExpiresDays) < DateTime.Now Then
                    If MessageBox.Show("Your password has expired! Please change your password.", My.Application.Info.Title, MessageBoxButtons.OK, MessageBoxIcon.Asterisk) = System.Windows.Forms.DialogResult.OK Then
                        ForcePassChange_.Show()
                        Exit Sub
                    End If
                End If
            End If
        Catch ex As Exception
            MessageBox.Show(ex.Message, My.Application.Info.Title, MessageBoxButtons.OK, MessageBoxIcon.Error)
        Finally
            Con.Close()
            Con.Dispose()
            rdr.Close()
        End Try


    End Sub