Using ADMT to migrate Win2K Forest to Win2K forest

I am looking for the best way to migrate some of the
users in a single domain forest to another single domain
forest. The section is being sold off and need to function
as per normal until a cutover date when the trusts between
the forests are broken ans then the new Foprest needs to
continue to provide access to all data resources exactly
as before. In short, I want to split a single forest into
2 forests with no impact on users.