Попробуй так, по клику формируется ссылка на основе select-ов думаю дальше сам подгонишь под свое.
<html>
<script type="text/javascript">
function Func(id_sel_1, id_sel_2, id_link) {
document.getElementById(id_link).href = '';
document.getElementById(id_link).href = 'somelink.php?';
// добавляем имя первого select
document.getElementById(id_link).href += document.getElementById(id_sel_1).name;
document.getElementById(id_link).href += '=';
// добавляем значение первого select
var n = document.getElementById(id_sel_1).selectedIndex;
document.getElementById(id_link).href += document.getElementById(id_sel_1).options[n].value ;
document.getElementById(id_link).href += '&';
// добавляем имя второго select
document.getElementById(id_link).href += document.getElementById(id_sel_2).name;
document.getElementById(id_link).href += '=';
// добавляем значение второго select
var n = document.getElementById(id_sel_2).selectedIndex;
document.getElementById(id_link).href += document.getElementById(id_sel_2).options[n].value ;
// Вывод =)
alert(document.getElementById(id_link).href);
}
</script>
<body>
<select id="sel_1" name="mm_1" class="inputs" style="width: 100px;">
<option value="1" selected="selected">January</option>
<option value="2">February</option>
<option value="3">March</option>
<option value="4">April</option>
<option value="5">May</option>
<option value="6">June</option>
<option value="7">July</option>
<option value="8">August</option>
<option value="9">September</option>
<option value="10">October</option>
<option value="11">November</option>
<option value="12">December</option>
</select>
<select id="sel_2" name="mm_2" class="inputs" style="width: 100px;">
<option value="1" selected="selected">January</option>
<option value="2">February</option>
<option value="3">March</option>
<option value="4">April</option>
<option value="5">May</option>
<option value="6">June</option>
<option value="7">July</option>
<option value="8">August</option>
<option value="9">September</option>
<option value="10">October</option>
<option value="11">November</option>
<option value="12">December</option>
</select>
<a id="link" href=somelink.php>Some Link</a>
<input type="button" onclick="Func('sel_1','sel_2','link')" value="Click me!">
</body>
</html>