Return Filtered Field

Hi,
I am using Cognos Impromptu and have an odd situation where a field
value filtered out need to reappear on a report.
    For instance I have 3 fields: Order number, Order type and Account
number. For every order number there is an attached Account number
except when the order type is ‘P' – for some reason this was not
entered!
How can I attached an account number to the P type Order Numbers?
    Most grateful in advance.

Sam