how to redefine an offical <OnEnter>?

[xmlover]

what i thought is to show my tooltip when mouse moves over the default EXPBar....

i check the offical MainMenuBar.xml

and found

<OnEnter>
        TextStatusBar_UpdateTextString();
        ShowTextStatusBarText(this);
        ExhaustionTick.timer = 1;
GameTooltip_AddNewbieTip(XPBAR_LABEL, 1.0, 1.0, 1.0, NEWBIE_TOOLTIP_XPBAR, 1);
       GameTooltip.canAddRestStateLine = 1;
</OnEnter>

hmmm,,,,which function should i hook.....once i thought to hook a EXPBar_OnEnter(),but now,i was confused......



if no results.....i will define a new frame over the default EXPBar..... but ...it's not what I want.....