External field on the approval policy

Hi,

When adding a level to an approval policy, under 'who are approvers' then 'determine from request', there is an option for 'External'.

I can't find any doco on, has anyone used it ? Current VRA approvals don't fit in with our internal workflows and I was hoping this field might be used to fire a vro workflow to return approver.

Any help much appreciated.

Cheers

Thomas