Check if file exist in folder? - powershell

Question

I'm not sure how to do this. I need to execute an script.
The script needs to watch a folder for files created. If the files are created it will trigger a series of functions.
But prior to that, the script must ALWAYS check if a certain file exist. Because otherwise the script will not execute. The existing file needs to be moved before doing anything else.
I tried using the filechanged event but it will overwrite the existing file...
Is there a way to do this?
Here is the beginning of the script:
$fsw = New-Object IO.FileSystemWatcher $folder, $filter -Property #{
IncludeSubdirectories = $true # <-- set this according to your requirements
NotifyFilter = [IO.NotifyFilters]'FileName, LastWrite'
}
$onCreated = Register-ObjectEvent $fsw Created -SourceIdentifier FileCreated -Action {
$path = $Event.SourceEventArgs.FullPath
$name = $Event.SourceEventArgs.Name
$changeType = $Event.SourceEventArgs.ChangeType
$timeStamp = $Event.TimeGenerated
Write-Host "The file '$name' at '$path'was $changeType at $timeStamp" -Fore white
$lineas = (Get-Content $root\UNB\TMP\FACT_TEMPORAL.TXT | Measure-Object -Line).Lines
Write-Host "El archivo contiene $lineas lineas" -Fore white
if ($lineas -gt 3) {
Write-Host "El archivo contiene información" -Fore white
limpia
leeyedita
printpdf
borrar
renombra
} else {
Write-Host "El archivo NO contiene información" -Fore white
borrar
}
}