If they were inserted manually into MyCostPro, they may be missing some required fields that are normally updated when the automatic update is run. Most likely the unique identifying field in the hidden column B "Item/Transaction ID (Unique)".
You dont need to fill this in with the same format data as the automatic download, but you would need to fill it in with UNIQUE data for your manual entries. For example, you could use just the transaction number, as long as you were sure it would never repeat.
note: The data that is automatically downloaded will never repeat.
Let me know if thats not the issue.
Thanks,
Scott