Since you mention jQuery, just select all the right nodes and check their text. You can put a regex in here if you want, but it's not needed.
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
<head>
<title>test</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<script type="text/javascript" src="http://jqueryjs.googlecode.com/files/jquery-1.3.2.min.js"></script>
<script type="text/javascript">
$( function(){
var texts = [];
$('b.blah').each( function()
{
var txt = $(this).text();
if ( 0 == txt.indexOf( 'Blah:' ) )
{
texts.push( txt.substr( 6 ) );
}
} );
alert( texts );
});
</script>
</head>
<body>
<b class="blah">Blah: Some Text 1</b>
<div id="foo"><b class="blah">Blah: Some Text 2</b>
<div id="foo"><b class="blah">Some Text 3</b>
</body>
</html>
Or with a string of HTML
$( function(){
var htmlChunk = '<b class="blah">Blah: Some Text 1</b>\n'
+ '<div id="foo"><b class="blah">Blah: Some Text 2</b></div>\n'
+ '<div id="foo2"><b class="blah">Some Text 3</b></div>';
var texts = [];
$('b.blah', '<div>' + htmlChunk + '</div>').each( function()
{
var txt = $(this).text();
if ( 0 == txt.indexOf( 'Blah:' ) )
{
texts.push( txt.substr( 6 ) );
}
} );
alert( texts );
});