The FSName line is still inside the
With .DataSource so you are saying .DataSource.DataSource.DataFields("Nomor Polis").Value
Try removing the red text from this chunk of your code
Code:
With .DataSource
.ActiveRecord = recordNumber
.FirstRecord = recordNumber
.LastRecord = recordNumber
FSName = .DataSource.DataFields("Nomor Polis").Value & " - " & .DataSource.DataFields("Nama Tertanggung").Value
End With