Unable to retrieve customfield values from NewList for a filter - Writing OTA Code in Excel

I’m trying to write a OTA code to import defects from a filter. It happens smooth when the field is a system field, but it doesn’t happen for user defined fields..

How do I do that? I have been trying it for while but I don’t see and progress

' Set the filter values.

    BugFilter.Filter("BG_STATUS") = "Closed"

    BugFilter.Order("BG_PRIORITY") = 1

  MsgBox BugFilter.Text

'Create a list of defects from the filter

' and show a few of them.

   Set buglist = BugFilter.NewList

   msg = "Number of defects = " & buglist.Count & Chr(13)

   For Each theBug In buglist

      msg = msg & theBug.ID & ", " & theBug.AIT& ", " & theBug.Status & ", " & theBug.Priority & Chr(13)

      i = i + 1

      If i > 10 Then Exit For

   Next

   MsgBox msg

If I have theBug.AIT (CustomFIeld) and run the script it gives an error. Without that it works just fine. All I can say is I have tried with the database column name to which is something linke BG_USER_** and it still didn't work.

Hope someone here can correct me if I'm doing something wrong here.