Here's how:

[lang='vb']Dim objNetwork, strPrintServer
Set objNetwork = WScript.CreateObject("WScript.Network")

strPrintServer = "\\Your_Print_Server"

Private function GetUserObject
On Error Resume Next
Set GetUserObject = GetObject("WinNT://"  objNetwork.UserDomain  "/"  objNetwork.UserName)
End function

set UserObject = GetUserObject

For Each Group in UserObject.Groups
Select case Group.Name
Case "Your_AD_Security_Group"
objNetwork.AddWindowsPrinterConnection strPrintServer  "\Your_Printer_Name"
End Select
Next[/lang]

To set the default printer:

[lang='vb']  Select case Group.Name
Case "Your_AD_Security_Group DEFAULT"
objNetwork.setDefaultPrinter strPrintServer  "\Your_Printer_Name"[/lang]

Job done.