If you set a object variable be sure that it's really set.
It's always a pleasure for a user to get a 'object variable not set' error box.

Dim session As New NotesSession

Dim db As NotesDatabase

Dim DecisionDoc As NotesDocument

Dim strID As String

Set db = session.CurrentDatabase

Set view = db.GetView("(IDs)")

Set DecisionDoc = view.GetDocumentByKey(id, True)

Call DecisionDoc.ReplaceItemValue("ShortName","1A")

Better Style:

Dim session As New NotesSession
Dim db As NotesDatabase
Dim DecisionDoc As NotesDocument
Dim strID As String
Set db = session.CurrentDatabase
Set view = db.GetView("(IDs)")
if not view is Nothing then
 Set DecisionDoc = view.GetDocumentByKey(id, True)
  if not DecisionDoc is Nothing then
    Call DecisionDoc.ReplaceItemValue("ShortName","1A")
  Else
    ErrorhandlingDecisionDoc
  End if
Else
  ErrorhandlingView
End if