how to customize the link between archivelink and Alfresco

hi,

We are using Alfresco as content manager and we want to scan the invoices according to the "Late Storage with Bar Codes in FI" scenario [http://help.sap.com/saphelp_470/helpdata/en/46/c4317ffc4b11d195650000e82deb58/frameset.htm].

Each scanned invoice will be stored in Alfresco as a pdf file and we want to be able to display it from the sap 'display FI document' transaction (thru 'environment' menu / Additional assignments/object links).

my question is how to make the bridge between sap archivelink and Alfresco for this display ?

how to customize link between archivelink and Alfresco ? Is it possible with customizing only or is it necessary to buy third party software ?

we are working in 4.7.