How to programmable approve/reject ap invoice workflow

Hi expert:

    I have an requirement that programmable approve/reject ap invoice workflow in plsql package. But I don't find any API to achieve this.

In current situation, when user initiate approval for ap invoices, the approver need to approve/reject the ap invoices one by one, which is much wasting time.

So we want to customized one concurrent program to approve the ap invoices in batch, which is based on the paramters values of concurrent program.

While I don't find any API to approve the ap invoice.

Can anyone help me?