function onclick(event : any) do
    "ID of selected customer := event.targetID";
    var t := this;
    var selCustomer := first(select Customer where Id = event.targetID);
    debug("onclick");
    if event.targetColumnCaption like "checked" then
        selCustomer.(Checked := not Checked);
        true
    else
        if event.targetColumnNum = 0 then
            true
        else
            false
        end
    end
end;
select Customer