Hi Victor,
when you click on f4 help in back end get_v_method will gets trigger. there is no particular event will generated when you click on f4 help.
if you debugg get_v_method after completion of this method courser will go to config class CL_CHTMLB_CONFIG_UTILITY in that CREATE_UI_ELEMENT will gets trigger.
there selected value will assign to that f4 field.
provide break-point into get_v_method and go to webui click on f4 field.
where as if you give f4 help as free style method ex : ( using thtmlb:inputfield ) we can provide onclient click event. then that event will gets trigger when ever your pressing f4 help.
example :
<thtmlb:inputField id = "PROSPECT"
showHelp = "X"
helpId = "CRM_GPM_BUPAP_HELP"
f4Title = "Partner general"
helpInputFields = "PROSPECT=PARTNER"
visible = "TRUE"
lastValuesDisabled = "FALSE"
helpOnClick = "PROSPECT"
helpOutputFields = "PROSPECT=PARTNER"/>
Thanks & Regards,
Srinivas.