upload file without new page

[p-m]

Hi,
Is it somehow possible, to use form-dialog or create-form with set-on-submit for uploading a file without :action "/new-page"?
I tried this, but without success:

(defun on-import (obj)
  (princ (form-multipart-data obj)))

(defun on-upload (obj)
  (with-clog-create obj
      (form (:bind form :encoding "multipart/form-data")
        (form-element (:file :name "filename"))
        (form-element (:submit :value "OK")))
    (set-on-submit form 'on-import)))

TIA for any help, Peter