I'd suggesting adding an element: http://web2py.com/book/default/chapter/07#Adding-extra-form-elements-to-SQLFORM
Or customizing the form: http://web2py.com/book/default/chapter/07#Custom-forms
I'd suggesting adding an element: http://web2py.com/book/default/chapter/07#Adding-extra-form-elements-to-SQLFORM
Or customizing the form: http://web2py.com/book/default/chapter/07#Custom-forms