Need A "static" Variable For Using Window.event.clientX

I'm trying to use the window.event.clientX value for positioning a
javascript routine, but I'm having trouble. When the javascript
routine comes up, it comes up in a certain position based on
window.event.clientX. However, the user could click on something in
the script display (say, like a menu, or a calendar, or something),
that my "refresh" (reload that same script but with different values).
Thus, the first time, it works perfectly, but thereafter, it sets the
new x,y values to the most recent window.event.clientX and
window.event.clientY positions. I want it ONLY USE the positions which
were first used.

Does this make sense? Ok, here is the code snippets:

// This is the javascript
function RollOver( Text )
{
HelpText = Text ;
HelpX = window.event.clientX;
HelpY = window.event.clientY;
ToShow = setTimeout( "DoRollOver()", 1, "JAVASCRIPT" );}

// This is the HTML
<input type="Text" name="timestamp1" value="">
<img src="myImage.gif" onmousedown="RollOver( getText() );">

The first time the image is clicked, the source comes up in the correct
place. But this new script that came up is now the current "event" so
when someone clicks on something to reload the script with a different
value, it sets the position relative to the lastest script placement,
not the original image.