Several Approvers Required

Guys:

I need to setup requisition approval to handle several approvers:

A requisitioner enters a requisition.

If requisition total  is lesst than 1000 then manager must approve it and goes to PO creation. Just one approver.

If requisition total is greater than 1000 and less than 5000, the manager must approve it, then plant manager must approve it, then controller must approve it and finally goes to PO creation. Three approvers required.

If requisition total is greater than 5000, the manager must approve it, then plant manager must approve it, then controller must approve it, then VP Operations must approve it and finally goes to PO creation. Four approvers required.