Displaying only changes when using get-content -wait - powershell

Question

I created the following function which I wanted to use for a very simple CTI solution I have to use at work. This CTI process is writing all received calls to a text logile.
This function starts a new powershell Job and checks if the .log has been saved during the last 2 seconds and gets the last 4 lines of the log (receiving calls always creates 4 new lines).
During the job update I'm using regex to find the line with the phonenumber and time and append this to a richtextbox in a form.
In theory this works exactly as I want it to work. If I manually add new lines and save the file, it's always showing the timecode and phone number.
In the field however, this doesn't work as the CTI process is opening the file and doesn't save the it unless the process is shutting down.
I know that I can use get-content -wait to display new lines. I already tested this in the console and it's displaying new lines as soon as the .log is updated from the CTI process. What I don't know is how to rewrite the function to work with that, displaying only new lines and not all the old stuff when first running the script. I need to keep it in the job for a responsive form. Another thing is, that the computer running the form, doesn't have that much power. I don't know if get-content -wait could cause high memory usage after several hours. Maybe there are also some alternative solutions for a case like that available?
function start-CTIlogMonitoring
{
Param ($CTIlogPath)
Write-Debug "startCTI monitor"
Add-JobTracker -Name "CTILogger" -ArgumentList $CTIlogPath `
-JobScript {
#--------------------------------------------------
#TODO: Set a script block
#Important: Do not access form controls from this script block.
Param ($CTIlogPath) #Pass any arguments using the ArgumentList parameter
while ($true)
{
$diff = ((Get-ChildItem $CTIlogPath).LastWriteTime - (get-date)).totalseconds
Write-Debug "diff $diff"
if ($diff -gt -2)
{
Write-Debug "cti log DIFF detected"
Get-Content -Path "$CTIlogPath" -Tail 4
Start-Sleep -Seconds 1
}
}
#--------------------------------------------------
}`
-CompletedScript { Param ($Job) }`
-UpdateScript {
Param ($Job)
$results = Receive-Job -Job $Job | Out-String # Out-String required to get new lines in RTB
#get the stuff from results and make it more appearing to read for humans
if ($results -match '(Ein, E, (\d+))')
{
Write-debug "Incoming Call:"
$time = ([regex]'[0-9]{2}:[0-9]{2}:[0-9]{2}').Match($results)
$phoneNumber = ([regex]'Ein, E, (\d+)').Split($results)[1]
Write-Debug "$time ----> $phoneNumber"
if ($richtextboxCTIlogs.lines.count -eq 0)
{
$richtextboxCTIlogs.AppendText("$time ----> $phoneNumber")
}
else
{
$richtextboxCTIlogs.AppendText("`n$time ----> $phoneNumber")
}
$richtextboxCTIlogs.SelectionStart = $richtextboxCTIlogs.TextLength;
$richtextboxCTIlogs.ScrollToCaret()
}
<#else
{
Write-Debug "found nothin"
}#>
}
}