Populate a input field with selected checkboxes

I have a website with a form. You can see it here: [login to view URL] (Idées de séjour in the header) There is 2 text input field (idees_sejour_selection1 and idees_sejour_selection2) If you click the grey arrow image, a drop-down menu open. In these drop-down, there is checkboxes. When you check checkboxes and you click "Confirmer" button, I want the corresponding input text field to be fill with text form selected checkboxes of the drop-down menu. The text must be pulled form the tag of the label of the checkboxes. Each text entry must be separated by a comma (,) These input text fields are just visuals indicator: their are not use for the search filter. The script must be versatile if we add checkboxes in the future. You can see a live example here: [login to view URL] In the "Suggested area" section.