Approval Hierarchies 11.5.10

There is a future requirement in our organisation that any orders over £20K are "rubber stamped" by a Head of Service.  Is it possible for this to be incorporated into an approval hierarchy?  We would still need the budget manager to approve the requisition, and I am not sure that it is possible to have a user in the hierarchy who does not take any action?

We could set our hierarchies so that everything over £20K went to a named person, but I suspect that this would mean that the approval would need to be done by them, and it is really only to approve the amount of spend, rather than approve the requisition.