entering info into a web form

My company has an internal web form that allows us to enter data on staged PC's.  I've found that the data can be entered automatically into the for if I specify it in the URL.  For example, one section prompts for "serial number".  The source looks like this:

<td colspan="3"><input type="text" name="serialnum" value=""></td>
     </tr>

and if I enter this into the URL:

htp://<companysite>/order/index.php?page=queue_staging .inc&editid=1595&serialnum5= xxxxxx

(Note:<companysite> is actually the name of our site and xxxxxx represents the serial number.  http was changed to htp so this rich text editor won't automatically translate it into a link)

It will print the information into the field automatically.  The problem I am having is that the fields appear multiple times within the same declared variable names and I can't find what I should put in the URL to make it fill in the  seocnd serialnum rather than the first.  Below are other snippets of the code which I think are likely culprits for declaring what part of tyhe form but I can't seem to find the proper syntax.

<form name="Queue0" method="post" action="/order/index.php?page=queue_staging.inc&editid=1 595" style="margin-bottom:0px">
    <input type="hidden" name="counter" value="0">

In these the number next to "queueX" advances with each section and the value for "counter" advances also, so the second one would have Queue1 and value="1" for the counter.

I have tried putting in the following into the URL

htp://<companysite>/order/index.php?page=queue_staging .inc&editid=1595&counter=1&serialnum5=xxxxxx

but it still places the info in the first serialnum area of the form.

In Cae anyone is wondering the "editid" section in the URL refers to the page, if it's changed then it just advnces to the next page, not the next section on the same page.

I hope someone out there can help me, please let me know if you'd like me to cut and pate more of a sample form to this site, I can even copy the whole source (although it's several pages long). 

Unfortunately I do not have that kind of access to our company website, and the whole place is caught up in so much red tape that it would take forever to get the code inserted (if I could get it in at all, I'm not officially a programmer at the company).  I am limited to either inserting a query string into the URL or somehow otherwise directly inserting the data into the form.  The ultimate goal of this process will be to create an automated script (CLS, KIX32, or VBS) which will insert the proper data onto the website.  It currently takes around 2 to 3 hours a day for me to do this.

   I hope someone has an idea of how this can be accomplished, please let me know if you want more sections of the source.