AjaxEventBehavior("onclick")

Hello
how to get status of keyboard in onclick handler, i mean status of ctrl
or alt keys?
i want to select multiple lines in my table using ctrl-click on lines.
i.ve found some solutions using overriden getCallbackScript, but it
seems it;'s working only in older wicket versions, after several hours
i've not found any working solution for wicket 6.
Thanks for any advice

boris