Cross talk threads to allow for file system access in powershell - multithreading

Question

Reference: Runspace for button event in powershell
https://www.foxdeploy.com/blog/part-v-powershell-guis-responsive-apps-with-progress-bars.html
So, I believe my issue is that PowerShell is unable to access the memory space of the file system, from within the memory block, of my thread, is there a way to solve this, to access the file system, from a multi-threaded application?
Back Story:
So, I run a program, that calls upon "code"/command, from the command prompt, (*.exe) (Robocopy) to copy files from a server, to a group of computers, at a time. We have a classroom environment, at my work, so I have my setup, in a way, that I have a folder, per room. I keep a list of all our addresses (static), for each room, in their perspective folders. We have an update, from our developers, that we need to push to all of the rooms. We need to run a slow push, as to not disturb the production environment. It's proprietary, so we can't use a/any typical solution(s), like Microsoft SCCM. So, I created a script to push to the rooms. while it does work, it's not a smooth operation. I'm not actually the one pushing the update, because of the slow process, of updating. I'm just trying to make a stable smooth-running package, for the person, who is going to be doing it. My code works, outside of the thread, (I) tested it, I know it works.
So how I came my conclusion of knowing, that my code works outside of the thread. (The picture) I followed the same setup, with my code, (A button click event inside of a thread, running the form). Placed the actual working code, (tried, and tested, before making a Thread, for the interface, after completing backend operation code testing.)
("Region Boe's Addition") referring to Boe Prox, (from the link)
In his, he is updating from a command line/powershell window, via a function run inside a thread. I'm running an event from a button, inside of a thread and trying to run a separate thread, for the click event(s). Outside of the thread. The event works fine, but inside, it doesn't work, at all..
Basic Code:
// Multi thread, thread for the $form, and thread for the event (as per referenced link)
$var = [PowerShell]::Create().AddScript({ button.Add_Click{
$var = [PowerShell]::Create().AddScript{<Thread><Robocopy></Thread>}
})

Answer 1

Needed the "Start-Process" -Wait command to allow for the listbox, to be updated in-between copies, to confirm installation, through each step in the loop.
$choice = $comboBox.SelectedItem
# $drive = Get-Location
if(!(Test-Path -PathType Container -Path "L:\$choice"))
{
# New-Item -ItemType "container" -Path . -Name $choice
New-Item -ItemType "Directory" -Path . -Name $choice
}
# $folder = $_
# Where is it being stored at?
[System.IO.File]::ReadLines("Y:\$choice\IPs.txt") | foreach {
ping -a -n 2 -w 2000 $_ | Out-Null
Test-Connection -Count 2 -TimeToLive 2 $_ | Out-Null
if($?)
{
RoboCopy /Log:"L:\$folder\$_.log" $source \\$_\c$\tools
RoboCopy /Log+:"L:\$folder\$folder-MovementLogs.log" $source \\$_\c$\tools
Start-Process -Wait "P:\psexec.exe" -ArgumentList "\\$_ -d -e -h -s cmd /c reg import C:\tools\dump.reg"
# Copy-Item -LiteralPath Y:\* -Destination \\$_\c$\tools
$listBox.Items.Add($_)
}
}