Glenn is absolutely correct in his assertion that installations during login is a bad idea. But since you are probably in a bind, I modified the code just a bit to make the copying and execution easier.

 Code:
$WFBSHInstaller = "Agent_Installer.msi"
$pathOfWFBSHInstaller = "\\SERVER\netlogon\Kix32\Apps\TrendMicro"
$pathOfLocalWFBSHInstaller = "%USERPROFILE%\Kix32\Apps\TrendMicro"
$strComputer = "."
$strOutput = ""
$serviceCount = 0
$totalServiceCountToCheck = 3

; check if WFBS-SVR is installed by detecting service ntrtscan, tmlisten, svcGenericHost are exist or not
$objWMIService = GetObject("winmgmts:{impersonationLevel=impersonate}!\\" + $strComputer + "\root\cimv2")
$colItems = $objWMIService.ExecQuery("Select * from Win32_Service")
For Each $objService in $colItems
  $strOutput = $strOutput + $objService.name + @CRLF
  Select
    Case $objService.name = "ntrtscan"
      $serviceCount = $serviceCount + 1
      ;? "Service " + $objService.Caption + " is " + $objService.Started
    Case $objService.name = "tmlisten"
      $serviceCount = $serviceCount + 1
      ;? "Service " + $objService.Caption + " is " + $objService.Started
    Case $objService.name = "svcGenericHost"
      $serviceCount = $serviceCount + 1
      ;? "Service " + $objService.Caption + " is " + $objService.Started
  EndSelect
Next

If $serviceCount <> $totalServiceCountToCheck
  Copy $pathOfWFBSHInstaller+"\"+$WFBSHInstaller $pathOfLocalWFBSHInstaller
  Shell "msiexec /qn /i "+$pathOfLocalWFBSHInstaller+"\"+$WFBSHInstaller
  If @error
    "the installer failed with error:" @error
    get $
  Endif
EndIf