Thanks Its working. I used as below as scripttext in invoke-vmscript.
$updateObject = New-Object -ComObject Microsoft.Update.Session
$updateSearcher = $updateObject.CreateUpdateSearcher()
$searchResults = $updateSearcher.Search("IsInstalled=0")
$timeoutValue = 1200
$startTime = Get-Date
while($searchResults.Updates.Count -ne '0' -and (New-TimeSpan -Start $startTime -End (Get-Date)).TotalSeconds -lt $timeoutValue){
Start-Sleep 1
$searchResults.Updates.Count
}
if((New-TimeSpan -Start $startTime -End (Get-Date)).TotalSeconds -ge $timeoutValue) {
'windows update completed Partially'
}
else{
'windows update completed sucessfully'
}