I need to be able to get the selected inputs from four different
selections and based on those 4 selections, post a part number in another text field (e21b)within the same form.


<div class="formcss1">
<form id="f29" >
<fieldset id="e29" class="cc46">
<p>
<label id="e28" class="cc47" for="e26"> Wheel Size </label>
<br>
<select id="e27" class="cc48" size="1" name="Title" title="Title">
<option value=101> 19.5"</option>
<option value=110> 22.5"</option>
<option value=120> 24.5"</option>
</select>

<label id="e25" class="cc47" for="e26"> Bolt Holes </label>
<select id="e26" class="cc48" size="1" name="Title" title="Title">
<option value=201> 8</option>
<option value=210> 10</option>
</select>
<br>
<label id="e24" class="cc47" for="e23"> Bolt Circle </label>
<select id="e23" class="cc48" size="1" name="Title" title="Title">
<option value=301> 6.5"</option>

<option value=310> 11.25"</option>
<option value=320> 170mm</option>
<option value=330> 275mm</option>
<option value=340> 335mm</option>

</select>
<label id="e22" class="cc47" for="e26"> Axle Type </label>
<br>
<select id="e21" class="cc48" size="1" name="Title" title="Title">
<option value=401> Steer</option>
<option value=410> Drive</option>

</select>
<label id="e25a" class="cc47" for="e26a"> Part No.</label>

<br>
<select id="e21b" class="cc48" size="1" name="Title" title="Title">
<option> 600-618</option>
<option> 600-628</option>
<option> 600-610</option>
<option> 600-620</option>
<option> 600-638</option>
<option> 600-648</option>
<option> 600-630</option>
<option> 600-640</option>
<option> 600-658</option>
<option> 600-650</option>
<option> 600-660</option>
<option> 600-690</option>
<option> 600-691</option>
<option> 600-670</option>
<option> 600-680</option>
<option> 700-720 </option>
<option> 700-718</option>
<option> 800-820 </option>
<option> 800-830</option>
<option> 900-910</option>
</select>
</fieldset>
</form>

var select1 = document.getElementById(e27).value;
var select2= document.getElementById(e26).value;
var select3 = document.getElementById(e23).value;
var select4 = document.getElementById(e21).value;
<e21b.option selected = var select5>;


if (select1.value 101 && select2.value= 201 && select3.value=330 && select4.value=401)
{
Then select5 ===600-618;
}
else if (select1.value = 101 && select2.value= 201 && select3.value=330 && select4.value=410)
{
Then select5 =600-628;
}
else if (select1.value = 110 && select2.value= 201 && select3.value=330 && select4.value=410)
{
Then select5 ===600-638;
}
else if (select1.value = 120 && select2.value= 201 &&select3.value=330 && select4.value=401)
{
Then select5 ===600-658;
}
else if (select1.value = 110 && select2.value= 210 &&select3.value=34 && select4.value=401)
{
Then select5 ===600-690;
}

</div>