下拉框加输入框的组合框

<div style="position:relative;">
<span style="margin-left:100px;width:18px;overflow:hidden;">
<select style="width:118px;margin-left:-100px" onchange="this.parentNode.nextSibling.value=this.value">
<option value="Tree.L"> Tree.L </option>
<option value="一颗树"> 一颗树 </option>
<option value="一颗树"> 一颗树 </option>
</select></span><input name="box" style="width:100px;position:absolute;left:0px;">
</div>