NTFS permission for a non-Domain user

I have a NT4 domain and a file/print server running on win2003sp1. note that this win2003 server is joined to my NT4 domain. the issue is I have an application server which is not part of the domain (as workgroup) and needs at least a write access to a folder on my file/print server. since i have set up ntfs permissions on my file/print server for my domain users, how can i add or grant ‘write’ access to a user which is not part or a member of the domain.