Hans, * using shapefiles, this isn't possible with mapserver (or at least I don't think so, someone correct me if not) * if you're using postgis, you could implement this with some server side scripting, with or without some help from the mapscript functions
I think the way to go for your case is geoserver and its wfs-t functionality: http://sigma.openplans.org:8080/geoserver/wfst_demo/wfs-t.html cheers, tb
