I have add the following to my report by it only list 0.

Begin Column
   FieldName = "Item.TagAlongItem"
   DrillDownFieldName = ""
   DrillDownReportName = ""
   StoreIDFieldName = ""
   Title = "Tag Along
   VBDataType = vbString
   Formula = "CASE When Item.TagalongItem = Item.id then Itemlookupcode Else 0 End"
   ColHidden = False
   ColNotDisplayable = False
   FilterDisabled = False
   ColWidth = 2460
   GroupMethod = groupmethodNone
   ColFormat = ""
   ColAlignment = flexAlignLeftCenter
End Column