standby only at login screen?

Question

I have 10 computers running Windows 7 connected to Active Directory. I would like to setup the computers so that they go into standby if no one logs in for 15 minutes, BUT I want the computers NOT to go into standby ever if someone is logged in.

This would involve the changing of Power Plans. Is there a way to have one Power Plan loaded when the computer is not logged in and a different Power Plan loaded when a user is logged in?

UPDATE: Using jscott's suggestions I think I have what I want working. I made a Power Plan called Logged_In for the User Configuration and Logged_Out for the Computer Configuration. The last glitch I had to fix was that Logged_In was applied after logout until the next policy refresh. I made the following script to run at logout based on code I found >here<:

Set objShell = WScript.CreateObject("WScript.Shell")
Set objWshScriptExec = objShell.exec("powercfg.exe -list")
Set objStdOut = objWshScriptExec.stdOut

While Not objStdOut.AtEndOfStream
   strLine = objStdOut.ReadLine
   If InStr(strLine,"Logged_Out") Then
      strGuid = Mid(strLine,20,37)
   End If   
Wend
objShell.run "powercfg.exe -setactive " & strGuid

Answer 1

The best way to do this is to create a GPO. You'll want to look under Computer Configuration, Preferences, Control Panel Settings, Power Option. Then right click and select New, Power Plan. From there you can specify all the power settings you want. Here is a technet article.

http://technet.microsoft.com/en-us/library/dd759141.aspx