User defined type not defined in vba factorytalk view

Question

I am new to VBA code, and working on a SCADA system where VBA code is required. I am having VBA code that need to be imported but getting errors as "User Defined Tags not Defined". Please tell me where I am wrong in the following code:

Option Explicit
Private lstRecHeader As ColumnHeader        ' Headers in the lstReceived
Private lstRecItems As ListItem             ' Items in the lstReceived
Private lstRecSubItems As ListSubItem

Getting error on the part Private lstRecHeader As ColumnHeader