[UnrealEd]

try a for loop to loop over the entries:

Code:

for( var i=0; i<number_of_entries; i++){
  window.opener.document.foo.attach{i}.value = document.filesform.userFile[i].value;
}

i'm not sure about the {} but if you search the web, i'm sure you'll find how to do so

Hope this helps,
UnrealEd