The real script I want to use is form1.mysubform.presence = "hidden";
It works run at client but not if I run it at server. If I use my form in a worklow, I need to run the script at server or at client ? I will test that. Thank you again Paul to take time to answer my silly questions :).
Remember that not all of the events will run server side ...is it possible that the event that you have chosen is not sunning server side? You can verify it by putting a value in a field on the event and if the field shows up and is populated than you know the server side script ran. Also if any errors are produced by your script they will appear in the system log.