I did a entries search using post for a quiz type feature in a web site I built back in February. I also wrote up the entire process here.
Copying and pasting a good section of that blog entry here:
First up, build a channel called quiz results. with five fields. The first for field types need to be drop downs - I called mine {question-one}, {question-two}, {question-three} and {question-four} and populated with the answers a, b, c each on a new line. The last field is a relationship field which will be the product that the results link to, I called this {question-result}. Now start the data entry creating entries for each possible combination of answers.
Next build a basic form with radio buttons for the answer. You'll also need some way to get the $POST data into the quiz results page to pull up the correct answer. I thought about using strait php, but didn't want to enable php on my templates so looked to devot:ee for an add-on and found a few. The one that I chose looked best and is dead simple to use: EvoPost.
Next you need to create a new template called evopost (or whatever you want it to be) and set the action="" to point to that template like this action="{site_url}/template_group/evopost" and then in the evopost template you add the following code where you prefix the name="" value of each field with ep_ so if your field is name="old" then your post data would be {ep_old}:
{exp:evopost:getpostdata}
{redirect="/treat-matchmaker/results/{ep_old}/{ep_big}/{ep_name}/{ep_foobar}"}
{/exp:evopost:getpostdata}
This then redirects to the results template where Where your channel entries tag then pulls this information from the url structure like this
{exp:channel:entries
channel="matchmaker"
search:question-one="{segment_3}"
search:question-two="{segment_4}"
search:question-three="{segment_5}"
search:question-four="{segment_6}"
disable="pagination|member_data"
}
To me this sounds almost exactly like what you need/want to do, except for the ajax part.