M365AppsWin32DetectionScript.ps1

#DetectionScript
function Write-LogEntry {
	param (
		[parameter(Mandatory = $true, HelpMessage = "Value added to the log file.")]
		[ValidateNotNullOrEmpty()]
		[string]$Value,
		[parameter(Mandatory = $true, HelpMessage = "Severity for the log entry. 1 for Informational, 2 for Warning and 3 for Error.")]
		[ValidateNotNullOrEmpty()]
		[ValidateSet("1", "2", "3")]
		[string]$Severity,
		[parameter(Mandatory = $false, HelpMessage = "Name of the log file that the entry will written to.")]
		[ValidateNotNullOrEmpty()]
		[string]$FileName = $LogFileName
	)
	# Determine log file location
	$LogFilePath = Join-Path -Path $env:SystemRoot -ChildPath $("Temp\$FileName")
	
	# Construct time stamp for log entry
	$Time = -join @((Get-Date -Format "HH:mm:ss.fff"), " ", (Get-WmiObject -Class Win32_TimeZone | Select-Object -ExpandProperty Bias))
	
	# Construct date for log entry
	$Date = (Get-Date -Format "MM-dd-yyyy")
	
	# Construct context for log entry
	$Context = $([System.Security.Principal.WindowsIdentity]::GetCurrent().Name)
	
	# Construct final log entry
	$LogText = "<![LOG[$($Value)]LOG]!><time=""$($Time)"" date=""$($Date)"" component=""$($LogFileName)"" context=""$($Context)"" type=""$($Severity)"" thread=""$($PID)"" file="""">"
	
	# Add value to log file
	try {
		Out-File -InputObject $LogText -Append -NoClobber -Encoding Default -FilePath $LogFilePath -ErrorAction Stop
		if ($Severity -eq 1) {
			Write-Verbose -Message $Value
		} elseif ($Severity -eq 3) {
			Write-Warning -Message $Value
		}
	} catch [System.Exception] {
		Write-Warning -Message "Unable to append log entry to $LogFileName.log file. Error message at line $($_.InvocationInfo.ScriptLineNumber): $($_.Exception.Message)"
	}
}

$LogFileName = "M365AppsSetup.log"
Write-LogEntry -Value "Start Office Install detection logic" -Severity 1
$RegistryKeys = Get-ChildItem -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall"
$M365Apps = "Microsoft 365 Apps"
# $M365AppsCheck = $RegistryKeys | Where-Object { $_.GetValue("DisplayName") -match $M365Apps } // Commented out as issues found
$M365AppsCheck = $RegistryKeys | Get-ItemProperty | Where-Object { $_.DisplayName -match $M365Apps }
if ($M365AppsCheck) {
    Write-LogEntry -Value "Microsoft 365 Apps detected OK" -Severity 1
    Write-Output "Microsoft 365 Apps Detected"
	Exit 0
   }else{
    Write-LogEntry -Value "Microsoft 365 Apps not detected" -Severity 2
    Exit 1
}