The easiest way is to make a cutin with 'click in menu to receive' and another with 'received', and of course a menu that says 'receive'. I know that is not what you want but... that's the best I can tell so far.
Another best option to make a big cutin with all rewards and remarked with the which one correspond today if you are available to get it, and click in the menu 'receive reward'.
PS: If you are good enough to make this script why wouldn't you make the simple sql query to know the "top 10" of t_event_points? xd
EDIT:
*cutin("<filename>", <position>
This command will display a picture, usually an NPC illustration, also
called cutin, for the currently attached client. The position parameter
determines the placement of the illustration and takes following values:
0 - bottom left corner
1 - bottom middle
2 - bottom right corner
3 - middle of screen in a movable window with an empty title bar
4 - middle of screen without the window header, but still movable
The picture is read from data\texture\유저인터페이스\illust, from both the
GRF archive and data folder, and is required to be a bitmap. The file
extension .bmp can be omitted. Magenta color (#ff00ff) is considered
transparent. There is no limit placed on the size of the illustrations
by the client, although loading of large pictures (about 700x700 and
larger) causes the client to freeze shortly (lag). Typically the size is
about 320x480. New illustrations can be added by just putting the new file
into the location above.
The client is able to display only one cutin at the same time and each new
one will cause the old one to disappear. To delete the currently displayed
illustration without displaying a new one, an empty file name and position
255 must be used.
// Displays the Comodo Kafra illustration in lower right corner.
cutin("kafra_07", 2);
// Typical way to end a script, which displayed an illustration during a
// dialog with a player.
mes("See you.");
close2();
cutin("", 255);
end;