This script may help. You can check if the UAC is enabled, and what level the prompt is set at.

Code:
alias uac {
  var %v = HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System\
  var %v = %v $+ $gettok(EnableLUA ConsentPromptBehaviorAdmin ConsentPromptBehaviorUser,$1,32)
  if ($com(uac)) .comclose uac
  .comopen uac WScript.Shell
  noop $com(uac,RegRead,3,bstr,%v)
  return $com(uac).result
}


$uac(1) will return 0 if UAC is disabled, 1 if enabled
$uac(2) will return a level from 0 to 3 for an admin account
$uac(3) will return a level from 0 to 3 for a normal user account

Note that UAC can be enabled with the prompt set to 0 for an admin account which will not pop up the dialog. It's up to you to work out how to use this info.