Hi Philippe, General advice: Your code is getting too complicated for dtml. You will do much better by calculating your list of options in a Python Script. For your first problem: The only way to specify constants in dtml is as python expressions. So you would need <dtml-let isSelected="'false'"> (A python expression for a string). For what you really need: The only way you can change a variable in dtml-let is if you can do it with an expression. An assignment is a statement, so you can't use it in dtml. You need something along the lines of <dtml-let isSelected="[]"> (an empty list is false) <dtml-if ...> <dtml-call "isSelected.append(1)"> (a non-empty list is true) </dtml-if> ... But you can do everything with <select multiple name="categories:list" size=10> <dtml-let selectedcats="getCategories()"> <dtml-in expr="getAllPortalCategories()"> <dtml-let aPortalCategory=sequence-item> <dtml-if "aPortalCategory in selectedcats"> <option selected> <dtml-var aPortalCategory> </option> <dtml-else> <option> <dtml-var aPortalCategory> </option> </dtml-if> ... HTH, Shai.