Hi makumbi,
You need to check the DataReader Item value with IsDBNull.
If its DBNull the set the value to Empty string and then compare with String.IsNullOrEmpty.
If String.IsNullOrEmpty(If(IsDBNull(RDR.Item("engrade")), String.Empty, RDR.Item("engrade"))) _
Or String.IsNullOrEmpty(If(IsDBNull(RDR.Item("engscore")), String.Empty, RDR.Item("engscore"))) Then
Dim cmd As New SqlCommand("UPDATE temp SET Division = @sc,Totalgrades = @sc2 WHERE admno = @admno")
cmd.Parameters.AddWithValue("@sc", "X")
cmd.Parameters.AddWithValue("@sc2", Nothing)
cmd.Parameters.AddWithValue("@admno", admno)
ExecuteQuery(cmd, "UPDATE")
End If