You can change the value of many, but not all, fields.
You can browse for a form using Design a Form if the type you want to edit is not open.
Open the form you want to edit and choose Design this form from the Developer tab or Tools, Forms menu.
(A video tutorial is here, if you need one: Enable the Developer ribbon) Show the Developer tab is on the first page. Outlook 2007: open the Office menu and go to Editor options. Outlook 2010: go to File, Options, Customize Ribbon and add a check to the Developer ribbon in the right pane. In Outlook 2007 and Outlook 2010, you need to show the Developer ribbon before you can open the form in design mode.
To open it, open any new form then go to Tools, Forms, Forms Designer (in older versions of Outlook). You can use the Forms designer to design custom forms for Outlook.
