Common field for CCK

Hi,

Is there some way, when I create a custom content type to flag a field as global (programaticaly or otherwise) between the created pages?
For example let's say the field in question is a file field, and I create "Page A" I select a file for the file field. Now if create "Page B"
the file field should be prepopulated with the file that I defined on "Page A" because they are of the same type. If I change the file
on "Page B" it should also change on "Page A".

Any ideas?

cheers