Limit Web Service Results to one first letter for alphabetic organizing

I have a site that draws its listings from a 3rd party web service and get all of the results at once in one long list. I want to limit the yield of info to all the items that start with a number or punctuation, a, b, c, d, e, etc per page. A whole page for listings starting with “A” and so, on. How do I do that? I can show you the link, but I don’t want to seem like I am shamelessly advertising in the forum.

The documentation for this web service is here:
But the documentation makes little sense to me since I hardly code JavaScript to this degree and everything seems out of context.

To make matters worse, the site I am working on is in ASPX with a masterpagefile. I usually use PHP, so my familiarity is once again limited.

If you need more info, I am glad to share.

<script language=“javascript” type=“text/javascript”>
document.write(‘<script language=“javascript” src="’+####+‘&sitenumber=’+#+‘&tid=event_names&pcatid=2&showcats=true&title=Concerts Tickets"></’ + ‘script>’);

Above is what the code calling this list looks like. It is a document.write method calling the third party service.

I want to sort my array to where it only calls one beginning letter at a time. So, for starters, just the letter ‘A’ for that page.

Anybody got any ideas?