With Lotusscript, you will always need to detach the file to the file system. You need to use a Java agent and something like getinputstream.
This was found with a simple google search and may help you, as you seem reluctant to write your own Java code:
http://www.hankos.net/A556E9/net.nsf/html/resources/how_to_read_a_text_file_attached_to_a_lotus_notes_document_without_detaching_it.html?OpenDocument