Client Tools :: Substitution Variables

How I go about writing a query that doesn't see the '&' symbol as a substitution character. The problem I have is:

select replace
( fnd_profile.value( 'XXBPO_URL')
, '&DOCID'
, ai_dfv.bpo__document_link
) document_link
from ap_invoices_all ai
, ap_invoices_all_dfv ai_dfv
where 1=1
-- where clause

The problem above is that instead of replacing the characters &DOCID with the required value, it is prompting for input.