Approval limits setup for AP invoice approval

Hello All,

I have a requirement to setup AP Invoice approval based on approval limits assigned to each person/job. Just like we setup the PO approval using approval groups and approval assignments where each person is assigned with a job and each job has an approval limit in $s. When PO is submitted for approval, we lookup the approval assigments and determine who has sufficient approval limit to approve that PO and place him as the approver in a approval group through AME.

Is there a similar setup for AP invoices? Is Signing Limits setup used only for Expense reports? As the Approval assignment setup does not have a document type for AP Invoice Approval, I am assuming that setup should not be used for invoice approval.