APINV Approval Workflow 11i - choose Approver ?

Dear All

my customer is on 11i and has this requirement about setup of AP Invoice Approval Workflow :

'the AP Clerk who enters the invoice should be able to determine who will be the approver of a specific invoice.

Namely, the AP Clerk should be able to assign in the invoice header the FND User (to be chosen from a predefined list) who is supposed receive the Notifiaction and give Approval to the Invoice'

Is this possible to be achived in 11i?

if yes, how? I am trying and use Action Type 'Final Authority .  Any hint which kind of Rule/Condition would apply for such a requirement?