[Javascript] Mouseover woes

[javascript@xxxxxxxxxx (Allen Wayne)]

Hi All,

heres a good one that has be slightly stumped. can I do a mouse over without
absolutly referencing the image???

eg 

<td class='box'><a href='test.asp'><img src='../images/bar.gif'></a></td>"

this is all I have I want to to the equivivent of 
<td class='box'><a href='test.asp'><img src='../images/bar.gif'
onmouseover='document.this.image.src=../images/test.gif'; return
true;'></a></td>"


ideas pointers???


Wayne