How to Query LDAP with a list of names for specific properties

I have a list of user names given to me, that I need to query Active directory to see the following:

- Account is a valid account in domain x, y or z

- Account has the property altsecurityidenties (pki certs mapped)

- Account has the property userPrincipalName (user logon)

Now I have this script to check for onesy and twosy accounts.  But I need to be able to modify this to go through a list of 100 user names or more.

$user = "username"

$rootdomain = [adsi] "LDAP://domainCN"

$searcher = New-Object DirectoryServices.DirectorySearcher $rootdomain

$searcher.Filter = "(samaccountname=$user)"

$result = $searcher.findOne().getdirectoryentry()

$result.altsecurityidenties   (if the user had pki certificates it will display.  if not then it wont)

$result.userPrincipalName

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Any help will be much appreciated

pfcjt@hotmail.com