Combination 'list_item' & 'image_button' PHP/JavaScript

[automation]

I have a web-page consisting of a listbox & image buttons. I want to post to the appropriate PHP script based on which list_item and image button combination is selected, where the logic is determined by JavaScript. So far, I can determine what list_item has been selected, but how do I determine what image button was selected?

The current PHP Script & JavaScript are below.

[HTML]<form method="post" action="operati on_request_navi gation.php" name="operation _navigation_for m" onsubmit=
"return operation()";>
<div id="Layer17" align="center">
<table height="89">
<tr>
<td align="center">
<b>
<font size="2">New Operation</b>
<select name="operation s_request_type" size="1" align="center">
<option selected="selec ted" >Select</option>
<option>Consult ant</option>
<option>Clien t Account</option>
</select>

</td>
</tr>
</table>

</div>
<div id="Layer18">
<table width="272" height="150" border="0" cellpadding="0" >
<tr>
<td width="89" height="67">&nb sp;</td>
<td width="177"><in put type="image" class="btn" id="Add" name="process_t ype" value="Add"
img src="images/Add.gif" alt="Add" width="126" height="37" /></td>
</tr>
<tr>
<td width="89">&nbs p;</td>
<td width="177"><in put type="image" class="btn" id="View" name="process_t ype" value="View"
img src="images/View.gif" alt="View" width="126" height="37" /></td></td>
</td>
</tr>
</table>

<table width="271" height="197" border="0" cellpadding="0" >
<tr>
<td width="89">&nbs p;</td>
<td width="176">
<a href="./logout_confirma tion.php">
<img src="images/Logout.gif" alt="Logout" width="126" height="37" border="0"/></td>
</tr>
</table>
</div>
</form>
<script>
function operation() {
var f = window.document .forms.operatio n_navigation_fo rm.elements[0];
var g = f.options[0].selected;
var h = f.options[1].selected;
var i = f.options[2].selected;
if(g) {
alert("Please select an Operation");
return false;
}
if(h) {
location.href=" ./consulting_sr_f orm.php";
return true;
}
if(i) {
location.href=" ./operations.php" ;
return true;
}
}
</script>[/HTML]

[acoder]

Add on onclick to each button to send the user to the corresponding page.