Append to AD User Account Description Property

How do I incoroporate this into the script below. I need to Append/Add to the AD User Accounts' description property

flagged for disablement with (Dor-Get-Date-IEM).

#My Script
cls
Import-module activedirectory
$90days = (get-date).AddDays(-90)
$filepath="C:\Temp\Dormant_Report_$(Get-Date -Format yyyyMMddmm).csv"
$splatter=@{
     Filter={
          enabled -eq $True
          -and lastlogondate -le $90days                      
          -and (employeeType -like 'E' -or employeetype -like 'C'  -or employeetype -like 'X' -or employeetype -like 'A' -or employeetype -like 'N')
      }
      Property=@(
                  'name',
                  'SurName',
                  'givenName',
                  'description',
                  'employeeType',
                  'employeeID',
                  'extensionAttribute15',
                  'lastlogondate',
                  'passwordlastset'
                )
}
$results=Get-ADUser @splatter
$results | Export-Csv $filepath -NoTypeInformation
$results | Disable-ADAccount -Whatif