Supplier Invoices/Bills - is there an option for "Approval"

Im looking for a solution to approving supplier invoices/bills. I work in an off-site office,  and I receive alot of supplier invoices to my email, which means the girls in he "onsite" office dont see them and cant check over the bills and approve - unless we email  back and forth which gets messy.

What I want to be able to do is find a simple solution.

I thought at first I could enter the bill as an "order" or a "quote", and then to approve they can convert to bill. Ie Bills showing in Bills are therefore approved. problem with this is  I cant seem to add a copy of the invoice to a quote or order, so they are unable to see the actual bill for reference. It seems I can only add an attachment to a "bill". 

Ideally I would like to

1. enter the bill into myob
2. attach a copy of the bill to file
3. girls onsite can then access Purchases from their end and they can tick "approved" or similar

Does anyone have any suggestions on an efficient way to do this? at the mooment, the only solution i can think of is to add as a bill, attach as a bill, and then once the girls have approved that they write that in the Suppler Invoice # section. The only problem with this is I think that will mess up the Duplicate invoice number function?

Any advice for an efficient solution would be great. Thanks