Position the tooltip

Position the tooltip

Here is my code that implements tooltips in my website:
var changeTooltipPosition = function(event) {
var tooltipX = event.pageX - 8;
var tooltipY = event.pageY + 8;
  jQuery('div.tooltip').css({top: tooltipY, left: tooltipX,'z-index': '120000'});
};
This works fine and displays the tooltip as a popup window bellow and to the right of the cursor while hoovering the button.
I'd like to modify the code so that the tooltip will appear just above the cursor(and the button, no change to the x dimension).
Is it possible and how?
Thx
I. Sher