PS C:\_scripts> .\change-appmaintenance.ps1 -PublishedApp "testdisable" -disable -Verbose

$wshell = New-Object -ComObject Wscript.Shell
$wshell.Popup("This application is unavailable because it is undergoing maintenance. Please try again later.",0,"APPLICAITON UNDER MAINTENANCE",0)

PS C:\_scripts> .\change-appmaintenance.ps1 -PublishedApp "testdisable" –Verbose

<#
.SYNOPSIS
	Disables (or re-enables) a published application by replacing the original command line with one that
 calls a pop-up window.
.DESCRIPTION
	Disables (or re-enables) a published application by replacing the original command line with one that
 calls a pop-up window. 

	It is recommended that this script be run as an a XenApp Farm administrator.
 This script assumes that the XenApp 6.5 powershell commandets are installed.
.PARAMETER PublishedApp
    Required parameter. Application that will be enabled or disabled.
.PARAMETER Disable
    Conditional parameter.
    If present, the application is disabled and maintenance message will be displayed. If not, then the maintenance message
    is removed and applicaiton is republished.
.EXAMPLE
	PS C:\PSScript > .\change-appmaintenance.ps1 -PublishedApp $PublishedApplicationName

	Script will try and re-enable the application.
 Will not display feedback
.EXAMPLE
	PS C:\PSScript > .\change-appmaintenance.ps1 -PublishedApp $PublishedApplicationName -verbose

	Script will try and re-enable the application.
 Will display feedback
.EXAMPLE
	PS C:\PSScript > .\change-appmaintenance.ps1 -PublishedApp $PublishedApplicationName -Disabled -verbose

	Script will disable the application.
 Will display feedback
.INPUTS
	PublishedApp maintenance file. If the file exists it assumes that the application was already put in maintenance. The script will read in the
    information from the file and take it out of maintenance (assuming the disabled flag is not present). It will delete the existing file if
    taking the application is taken out of maintenance.
.OUTPUTS
	A maintenance file will be generated per application (assuming the disabled switch is present). The file will contain the original location of the application from the published application
    properties, the name of the script runner, and the date the change was made.
.NOTES
	NAME: change-appmaintenance.ps1
	VERSION: 1.00
    CHANGE LOG - Version - When - What - Who
                 1.00 - 08/15/2014 - Inititail script - Alain Assaf
	AUTHOR: Alain Assaf
	LASTEDIT: August 15, 2014
.LINK
 http://www.linkedin.com/in/alainassaf/
 http://wagthereal.com
 http://gallery.technet.microsoft.com/scriptcenter/PowerShell-Message-Box-6c6e4f75
#>

Param(
    [parameter(Position = 0, Mandatory=$true )]
    [ValidateNotNullOrEmpty()]
	[string]$PublishedApp,

    [parameter(Position = 1, Mandatory=$False )]
    [ValidateNotNullOrEmpty()]
    [switch]$Disable)

### FUNCTION: get-mysnapin ####################################################
Function Get-MySnapin {
    Param([string]$name)
    if(-not(Get-PSSnapin -name $name)) {
        if(Get-PSSnapin -Registered | Where-Object { $_.name -eq $name }) {
            add-PSSnapin -Name $name
            $true
        } #end if module available then import
        else { $false } #snapin not available
        } # end if not snapin
    else { $true } #snapin already loaded
}
### FUNCTION: get-mysnapin ####################################################

#Constants
$datetime = get-date -format "MM-dd-yyyy_HH-mm"
$Domain=(Get-WmiObject Win32_ComputerSystem).Domain
$ScriptRunner = (get-aduser $env:username | select name).name
$XAZDC = "XenApp65ZDC.local"
$appmaintfolder = "C:\_scripts\appmaintenance"
$PSSnapins = ("Citrix.XenApp.Commands")
$XApps = New-Object System.Collections.ArrayList

#Populate XApps
foreach ($a in $PublishedApp) {$XApps.Add($a)>$null}

#Import Snapin(s)
foreach ($snapin in $PSSnapins) {
    if (!(get-MySnapin $snapin)) {
        write-verbose "$snapin PowerShell Cmdlet not available."
        write-verbose "Please run this script from a system with the $snapin PowerShell Cmdlets installed."
        exit
    }
}

#Confirm application(s) exists
foreach ($apps in $XApps) {
    $appresult = Get-XAApplication -ComputerName $XAZDC -BrowserName $apps -ErrorAction SilentlyContinue
    if ([boolean]($appresult)) {
        write-verbose "$apps exists"
        if ($Disable) {   #Disable flag is present
            $appmaintfile = $apps + ".txt"
            if (test-path -Path $appmaintfolder\$appmaintfile) {
                write-verbose "$appmaintfile already exists. Please confirm application name. No changes made"
            } else {      #Create maintenance file and replace app's command line
                add-content -Value $appresult.CommandLineExecutable -Path $appmaintfolder\$appmaintfile
                Add-Content -Value $ScriptRunner -Path $appmaintfolder\$appmaintfile
                Add-Content -Value $datetime -Path $appmaintfolder\$appmaintfile
                Set-XAApplication -computername $XAZDC -BrowserName $apps -CommandLineExecutable "powershell.exe -noprofile -executionpolicy bypass -command c:\_scripts\Show-appmaintenancebox.ps1"
            }
        } else {          #Read maintenance file and restore app's command line
            $appmaintfile = $apps + ".txt"
            if (test-path -Path $appmaintfolder\$appmaintfile) {
                $fileinfo = get-content -path $appmaintfolder\$appmaintfile
                Set-XAApplication -computername $XAZDC -BrowserName $apps -CommandLineExecutable $fileinfo[0]
                remove-item -Path .\appmaintenance\$appmaintfile
                Write-Verbose "Application maintenance removed for $apps"
            } else {
                write-verbose "*** ERROR *** expected maintenance file:$appmaintfile is missing. Please confirm application name. Script will exit"
                exit
            }
        }
    } else {
        Write-Verbose "$apps does not exist"
    }
}