iwp and portal and popup menu

[JFR]

Having a frustrating time, wondering if anyone has encountered this: very simple database, a user is adding a portal row, one field has popup menu of dates (from today back 20 days). Obviously the other existing portal rows are in editing mode - and if the existing dates in the othe other rows are older than the popup menu dates, the data is erased when submitted (the new row is obviously fine, as they can only choose from the popup menu of dates). Any ideas/workarounds?