PLUGIN SUGGESTION – Search for multiple custom field values

Does anyone know of a plugin that lets the user filter/search for posts based upon multiple custom field values but where the options in the second selection box are limited by what’s been entered in the first?

To give a little more information, I’m trying to set up a site to do with finding your ideal job and there will be a blog post about each job. Each post will have custom fields to categorise it by, for example, location, permanent/temporary and average salary.

I’d like the user to be able to search each of these custom fields to find jobs that are of interest. Don Benjamin’s “WP Custom Search” works very nicely for this BUT there’s an additional requirement.

I don’t want the user to go through the frustration of selecting each box to repeatedly find that there aren’t any results. Say for example, that the first custom field to choose is “Location” with a value of either “UK” or “Abroad” and that the second choice is “Job Term” which can be “Temporary” or “Permanent”. Let’s also assume that there are no “Permanent” jobs that are based “Abroad” (no posts that have both a “job-term” custom field value of “Permanent” AND a “location” custom field value of “abroad”). In this case, I’d like “Abroad” to disappear as an option in the second drop-down if “Permanent” is selected in the first drop down.

Does anyone know of a plugin that allows this kind of thing to be done? I’m not overly experienced at this whole WordPress thing but would be willing to have a crack at editing code if somebody can tell me what to do!

Thanks in advance,

Ross