Send HTML Email and newest file attachment from multiple paths

i got this script from Microsoft technet..

I need it to email and attach the NEWEST FIle or recent modified file in the folder path...

###############################################################################

###########Define Variables########

$fromaddress = "donotreply@labtest.com"
$toaddress = "Aishwarya.Rawat@labtest.com"
$bccaddress = "Vikas.sukhija@labtest.com"
$CCaddress = "Mahesh.Sharma@labtest.com"
$Subject = "ACtion Required"
$body = get-content .\content.htm
$attachment = "C:\sendemail\test.txt"
$smtpserver = "smtp.labtest.com"

####################################

$message = new-object System.Net.Mail.MailMessage
$message.From = $fromaddress
$message.To.Add($toaddress)
$message.CC.Add($CCaddress)
$message.Bcc.Add($bccaddress)
$message.IsBodyHtml = $True
$message.Subject = $Subject
$attach = new-object Net.Mail.Attachment($attachment)
$message.Attachments.Add($attach)
$message.body = $body
$smtp = new-object Net.Mail.SmtpClient($smtpserver)
$smtp.Send($message)

#################################################################################