Passing HTML via hidden value field

Hi all,
I'm currently using the following function to pass a value to a hidden form field:

add_filter('gform_field_value_inquiry_list', 'populate_inquiry_list');
function populate_inquiry_list($value) {
if(function_exists('upb_list_bookmarks')) {
return upb_list_bookmarks();
}
}

What this essentially does is return a function for the value of the inquiry_list parameter. If I set this as something as simple as:

return 'test';

it works just fine -- but since I am passing HTML data (which is what upb_list_bookmarks does) it doesn't seem to be saving the data at all - it's in-fact stopping the form from submitting. I've tested the function itself and it does return the information I want (again, an HTML ul>li list with URLs) and have even tested it by adding that to a sample textarea field, which works fine. It's this hidden field that I'm having trouble with. Do I need to somehow escape the HTML values for a hidden field? I'm ultimately looking for this form to be able to send the notification email to admins with that HTML list (which is generated per user). Any help would be greatly appreciated. Thanks!

Hi David,
Thanks for the link - unfortunately, nothing changed with that. This is what the output looks like (of that function):

<ul class="upb-bookmarks-list"><li class="upb_bookmark bookmark-273"><a href="http://yhmags.com/wordpress/moulding-profiles/profile-1/" class="upb_bookmark_link" title="Profile 1">Profile 1</a> - <a href="#" class="upb_del_bookmark upb_del_bookmark_273" rel="273" title="Remove this Bookmark">Delete</a></li></ul>

Hi David,
The Gravity Forms filter I'm using is referenced in my original question (I'm actually using this inside of a plugin). More specifically, I'm using http://codecanyon.net/item/user-bookmarks-for-wordpress/544129 to store the list of bookmarks. Let me know if that clarifies things or if I'm just making things more difficult :) Thanks.

Hi David,
Any other info you need? Thanks.

Hi David,
So - that function definitely seems useful, just doesn't seem to be doing what it's advertised to do, unless I'm missing some type of priority setting. Here's what I have:

add_filter("gform_allowable_tags_1", "allow_basic_tags");
function allow_basic_tags($allowable_tags){
	return '<p><a><strong><em><ul><li>';
}
add_filter('gform_field_value_inquiry_list', 'populate_inquiry_list');
function populate_inquiry_list($value) {
	if(function_exists('upb_list_bookmarks') && is_user_logged_in()) {
		return htmlspecialchars(upb_list_bookmarks($delete_link=false),ENT_QUOTES);
	}
}

So - I'm allowing the ul,li and a tags in the form (with a form ID of 1) and am then adding in that function -- but same result. Is a priority needed, or can you see anything else in the way? Thanks.