Filewatcher - catching multiple events issue - powershell

Question

I have a script that watches for files and triggers events on things like change. It works except there are duplicate events triggered for the same file (previous Stackflow question) which I need to handle. I am writing the filename to a logfile and only re-logging it if it is not in there.
The problem is I think the events are being fired synchronously and I am getting 2 entries in the log for 1 file change even though I am checking for dups. I am not sure how to work around this.
Here is the code:
Unregister-Event FW*
$source = 'S:\FIS-BIC Reporting\Report Output Files\IT\'
$filter = '*.*'
$MasterFile = "H:\PS\EmailNotifications.csv"
$LogFile = "H:\EmailNotify.log"
$FilesToCheck = import-csv -path $Masterfile
if (! (Test-Path $Logfile))
{
$Output = "Date|Filename|FilenameSpec|Email"
$Output | Out-File $LogFile
}
function Get-CharRight($str,$chars)
{
return $str.Substring($str.Length – $chars, $chars)
}
function ProcessFile()
{
param ([string]$filename)
Write-Host "file: $filename"
$ext= (Get-CharRight $filename 3)
if ($ext -ne "tmp")
{
foreach($FileToCheck in $FilesToCheck)
{
if($filename -like $FileToCheck.FilenameSpec)
{
Write-Host "Match"
#check log to see if an email was already sent
$Exists = import-csv -path $Logfile -delimiter "|" | where-object {$_.Filename -eq $filename}
Write-Host ($Exists.Count -eq $null)
if ($Exists.Count -eq $null)
{
Write-Host "Not in logfile"
$Date = Get-Date -format G
$Output = $Date + "|" + $filename + "|" + $FileToCheck.FilenameSpec + "|" + $FileToCheck.Email
$Output | Out-File $LogFile -append
}
else
{write-host "duplicate"}
}
}
}
}
$fsw = New-Object IO.FileSystemWatcher $source, $filter -Property #{IncludeSubdirectories = $true; NotifyFilter = [IO.NotifyFilters]'FileName, LastWrite, Attributes'}
Register-ObjectEvent $fsw Changed -SourceIdentifier FWFileChanged -Action {
ProcessFile $Event.SourceEventArgs.FullPath
}
Register-ObjectEvent $fsw Created -SourceIdentifier FWFileCreated -Action {
ProcessFile $Event.SourceEventArgs.FullPath
}
while($true) {
start-sleep -s 2
}
`