Define the radio button against the database item and this functionality should happen automatically.

and you should add radio button as u require on same radiogroup.
steps:

first create database i.e
CREATE TABLE GENDER(GEN CHAR(1));
-- This is only for testing.
now go to form builder open and do process

1) take new module(for testing)
2) go to navigator
2)create data block(use data block wizard)
3)go to layout editor(press f2)
4)make text item -- radio group( go to properties and make as radio group)
5)drag and drop two radio button from toolbar and set same group
6)drag and drop a command button- got to pl/editor- (when_button_press)- commit_form;


set property
-------------------
level-M
radio button value-M

radio-group propertis
---------------------
initial value- M