Script to Find latest Modify date, and email alert if last modify is older than 4hrs or so

Question

So, I want to monitor a directory, and get an alert if any file in the directory was not modified in the last, 4 hours or so.  
I think I'm on the right track, but I'm missing some pieces here.  Any suggestions?
Here's what I got so far:
::Set time and date to use later if needed
set currentTime_Date=%time% %date%
::For loop to pull the last file (I can't seem to pull the last modify time/date with it... this is where I need a hand)
FOR /F "delims=" %a IN ('DIR "*.*" /B /O:D') DO SET NewestFile=%a 
::Email latest file using blat
blat.exe -to [email protected] -server [email protected] -f [email protected] -subject "File Checker" -body "test" -attach %NewestFile%
(Not sure if I can use the variable for my newest file here or not)
Any suggestions?

Answer 1

Upgraded to V4 PS, and same error with this script (Note you had the variables and first function doubled up)
$folder='C:\v1\temp'
$Logfile = "C:\PicksheetMonitoring\WhileLoop.log"
function logit($msg){
$msg='[{0}]{1}' -f [datetime]::Now, $msg
$msg|Out-File $logfile -append
logit 'Running check'
if([datetime]::Now - (Get-Item $folder).LastWriteTime -gt [timespan]'0:4:0:0'){
Send-MailMessage -to "Picksheet Analysis <[email protected]>" -from "Picksheet Alerting <[email protected]>" -subject "It's been at least 4 hours since last Automation run" -smtpserver "exch01.domain.com" ..
logit 'alert sent'
}else{
logit 'all files good'