Setting the date to update when a submit button is used

Hello,

I am currently having issues with setting the date on a from. I can get the form to update the date everytime the form is opened, however I would like it to update every time the submit button is used. this is the code I currently have although it doesnt do exactly what i require:

var fld = this.getField("Today"); fld.value = util.printd("dd/mm/yyyy",new Date());