If you want a Field on your Custom Form to have changes made to it tracked in Updates, you will need to go to the specific Custom Form itself. Then, click on that specific Field on that Custom Form. In the left hand side, where the Field Settings are shown, down at the bottom, there is a header called: "Additional settings that affect this form only". Under that header, there is a setting called: "Display field changes in update feeds".
Once you click on that setting for that Field on that Custom Form, field changes made to that Field will display in the Updates section of a Project. (I have this activated for a Field on one of my Custom Forms; the Field is a drop down.)
Hopefully, this helps you out and is what you were looking to do. Terry Hynd EBSCO Information Services
