How to prevent specifying an "ended" Release or Cycle in a Defect

Function Bug_FieldCanChange(FieldName, NewValue)
  If FieldName = "BG_DETECTED_IN_REL" Then
     If RetrieveTR(NewValue) = True Then  'pass the name of the release
        Bug_FieldCanChange = DefaultRes
     Else
        msgbox "Release End Date has passed" & vbcrlf & vbcrlf & "Select a valid Release"
        Bug_FieldCanChange = False
     End If
  ElseIf FieldName = "BG_DETECTED_IN_RCYC" Then
     If RetrieveTC(NewValue) = True Then  'pass the name of the release
        Bug_FieldCanChange = DefaultRes
     Else
        msgbox "ReleaseCycle End Date has passed" & vbcrlf & vbcrlf & "Select a valid ReleaseCycle"
        Bug_FieldCanChange = False
     End If
  Else
     Bug_FieldCanChange = DefaultRes
  End If
End Function

Function RetrieveTR(RelName)
     Set relFactory = TDConnection.ReleaseFactory
     set RelFilter=   relFactory.filter
     RelFilter.filter("REL_NAME")="""" & RelName & """"
     Set listOfReleases = RelFilter.NewList
     Set ReleaseItem= listOfReleases.item(1)
     If ReleaseItem.DaysLeft > 0 Then
        bolAllowed = True
     Else
        bolAllowed = False
     End If
     RetrieveTR=bolAllowed
End Function

Function RetrieveTC(CycleName)
      Set cycFactory =TDConnection.CycleFactory
      Set cycFilter = cycFactory.Filter
      CycFilter.Filter("RCYC_NAME" ) = """" & CycleName & """"
      Set listOfCycles = CycFilter.NewList
      Set CycleItem= listOfCycles.item(1)
      If CycleItem.DaysLeft > 0 Then
        bolAllowed = True
     Else
        bolAllowed = False
     End If
     RetrieveTC=bolAllowed
End Function