can we add new approver while an approval process going on for Resigntion approvals?

we want to add an approver based on HR inputs for termination date.

If HR selected termination date prior to notification date then one more approver should come for that case. Else approval should be completed with HR only as final approver.

How can we achieve this? Can we add an approver in the middle of an approval process ?

Thanks,

Dara Nagasai