Access Denied when waiting for a Process started with Credentials - powershell

Question

I have a script which runs in a user context of a user that does not have permission to Install Applications. I need to install an exe, so I need to do it as a domain admin.
After the Installation I'd like to do other stuff in the script, but the Installation must be finished before continueing with the script.
When I Wait-Process for the installation to end, I get an access denied error.
Is there a way to wait for a Process to finish, which was started on another user context?
This is my code:
$P = Start-Process $Pfad\vcredist_x64.exe -Argumentlist "/install","/passive","/norestart" `
-WorkingDirectory $Pfad -Credential $cred -PassThru | Wait-Process
This are the error messages (translated from german):
Access denied
Wait-Process : This command terminated the "vcredist_x64 (6284)" operation due to the following error: Access denied. In Zeile:6
Zeichen:84
+ ... -WorkingDirectory $Pfad -Credential $cred -PassThru | Wait-Process
+ ~~~~~~~~~~~~
+ CategoryInfo : CloseError: (System.Diagnost... (vcredist_x64):Process) [Wait-Process], ProcessCommandException
+ FullyQualifiedErrorId : ProcessNotTerminated,Microsoft.PowerShell.Commands.WaitProcessCommand
Timeout issue
Wait-Process : This command terminated the process because the "vcredist_x64 (6284)" process was not completed within the specified timeout. In Zeile:6 Zeichen:84
+ ... -WorkingDirectory $Pfad -Credential $cred -PassThru | Wait-Process
+ ~~~~~~~~~~~~
+ CategoryInfo : CloseError: (System.Diagnost... (vcredist_x64):Process) [Wait-Process], TimeoutException
+ FullyQualifiedErrorId : ProcessNotTerminated,Microsoft.PowerShell.Commands.WaitProcessCommand

Answer 1

Posting my earlier comment as an answer
$proc = Start-Process "Notepad.exe" -PassThru
$proc.WaitForExit()
$proc1 = Start-Process "Calc.exe" -PassThru
$proc1.WaitForExit()

Answer 2

I did something like this the other day. My case was a little different. I was kicking something off, I wanted something to happen once that process ended, in the meantime I was doing another thing. For that, I used an event. Here is an example using Notepad:
$do_other_stuff = {
Write-Host 'Do Other Stuff'
Get-EventSubscriber | Unregister-Event
}
$p = Start-Process notepad.exe -PassThru
...do other stuff...
$job = Register-ObjectEvent -InputObject $p `
-EventName Exited `
-SourceIdentifier notepad `
-Action $do_other_stuff
If I wanted to wait for the even to trigger, I'd use Wait-Event. Stuff whatever you want done once the installer finishes running in the $do_other_stuff script block.
To your question, the following worked for me:
$p = Start-Process notepad.exe -PassThru -Wait
...do stuff...
As did...
$p = Start-Process notepad.exe -PassThru
$p.WaitForExit()
...do stuff...
These cases worked when running the script in elevated and un-elevated context. It worked when passing credentials to Start-Process via the -Credential parameter. I wasn't able to try it where the account calling Start-Process is a low privileged account; I have a meeting in a few, sorry.