Ho provato a fare come hai scritto ma sicuramente sbaglio qualche cosa...
Nello script la function modifyimage la devo sostituire con la function loadTwoImage oppure le matengo entrambe?

Cmq ti posto il codice di quello che ho fatto così forse ti aiuto a capire di più il mio problema:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">

<head>

<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>mia pagina</title>
<link href="css/style.css" rel="stylesheet" type="text/css" />

<script type="text/javascript">
//Specify image paths and optional link (set link to "" for no link):
var dynimages=new Array()
dynimages[0]=["photo1_1.jpg", ""]
dynimages[1]=["photo1_2.jpg", ""]
dynimages[2]=["photo2_1.jpg", ""]
dynimages[3]=["photo2_2.jpg", ""]
dynimages[4]=["photo3_1.jpg", ""]
dynimages[5]=["photo3_2.jpg", ""]

//Preload images ("yes" or "no"):
var preloadimg="no"

//Set optional link target to be added to all images with a link:
var optlinktarget=""

//Set image border width
var imgborderwidth=0

//Optionally, change 1.0 and 0.7 below to affect Wipe gradient size and duration in seconds in IE5.5+:
var filterstring="progidXImageTransform.Microsoft.GradientWipe(GradientSiz e=1.0 Duration=0.7)"

///////No need to edit beyond here/////

if (preloadimg=="yes"){
for (x=0; x<dynimages.length; x++){
var myimage=new Image()
myimage.src=dynimages[x][0]
}
}

function returnimgcode(theimg){
var imghtml=""
if (theimg[1]!="")
imghtml='<a href="'+theimg[1]+'" target="'+optlinktarget+'">'
imghtml+='[img]'+theimg[0]+'[/img]'
if (theimg[1]!="")
imghtml+='</a>'
return imghtml
}

function modifyimage(loadarea, imgindex){
if (document.getElementById){
var imgobj=document.getElementById(loadarea)
if (imgobj.filters && window.createPopup){
imgobj.style.filter=filterstring
imgobj.filters[0].Apply()
}
imgobj.innerHTML=returnimgcode(dynimages[imgindex])
if (imgobj.filters && window.createPopup)
imgobj.filters[0].Play()
return false
}
}
function loadTwoImage(0, 1){

modifyimage('dynloadarea1', 0);
modifyimage('dynloadarea2', 1);

return false;
}
</script>

</head>

<body onload="return modifyimage('dynloadarea1', 0);">
<table width="970" border="0" align="center" cellpadding="0" cellspacing="0">
<tr>
<td align="left" valign="top"><table width="970" border="0" cellspacing="0" cellpadding="0">
<tr>
<td width="295" align="left" valign="top"><table width="100%" border="0" cellspacing="0" cellpadding="0">
<tr>
<td height="50" align="left" valign="top"></td>
</tr>
<tr>
<td height="795" align="left" valign="top" class="box_01">

<a href="#" onClick="return modifyimage('dynloadarea1', 0);">

[img]p1.jpg[/img]</a>

<a href="#" onClick="return modifyimage('dynloadarea1', 2);">

[img]p2.jpg[/img]</a>

<a href="#" onClick="return modifyimage('dynloadarea1', 4);">

[img]p3.jpg[/img]</a>

</td>
</tr>
</table></td>
<td width="20" align="left" valign="top"></td>
<td width="655" align="left" valign="top"><table width="100%" border="0" cellspacing="0" cellpadding="0">
<tr>
<td height="160" align="left" valign="top"></td>
</tr>
<tr>
<td height="30" align="left" valign="top"></td>
</tr>
<tr>
<td align="left" valign="top"><table width="655" border="0" cellspacing="0" cellpadding="0">
<tr>
<td width="320"><table width="100%" border="0" cellspacing="0" cellpadding="0">
<tr>
<td height="320" align="left" valign="top" class="box_01">

<div id="dynloadarea1" style="width:80px;height:200px">

</td>
</tr>
<tr>
<td height="15" align="left" valign="top">[img]img/spacer.gif[/img]</td>
</tr>
<tr>
<td height="320" align="left" valign="top" class="box_01"></td>
</tr>
</table></td>
<td width="15"></td>
<td width="320" align="left" valign="top"><table width="100%" border="0" cellspacing="0" cellpadding="0">
<tr>
<td height="320" align="left" valign="top" class="box_01"></td>
</tr>
<tr>
<td height="15" align="left" valign="top">[img]img/spacer.gif[/img]</td>
</tr>
<tr>
<td height="320" align="left" valign="top" class="box_01">

<div id="dynloadarea2" style="width:80px;height:200px">

</td>
</tr>
</table></td>
</tr>
</table></td>
</tr>
<tr>
<td height="30" align="left" valign="top"></td>
</tr>
</table></td>
</tr>
</table></td>
</tr>
<tr>
<td align="left" valign="top"></td>
</tr>
<tr>
<td align="left" valign="top"></td>
</tr>
</table>
</body>
</html>