You cannot create those two listbox easily. But you can use an slider/calendar object populating variables that will be used in the expressions based on your master date field. Check this application that solves that issue.
Hope that helps.
Thanks for your hint, I don't know if I can use it in my situation. In fact my periods have the following synthax "ACTUAL - 2011.03" (data type, then minus sign then month dot and year) I have only 2 data types ACTUAL and TARGET. So 2 listboxes with those "data type-period" variables sorted by load order (I take care to load them in correct order) would be the best. Using calendar object could be difficult, because my periods are not so in date format...