How to choose the text encoding when importing text in Quark XPress 7

Hi there,
I’m trying to solve this puzzle: I want to import a plain text file (with XPress tags, but that’s not important) into a Quark XPress document. The usual AppleScript command to use is this:

tell document 1
set story 1 to alias myfile --(where myfile is a variable with the alias to the file I want to import)
end tell

This command will import the text, but does not allow me to specify which encoding the text file uses. Now, when you import text from the XPress GUI, there is an encoding menu available in the open dialog, so XPress supports this function. I just can’t find a way to access it from AppleScript. Any ideas?