给出以下CSS：

div.listBoxMoverUserControl
{
    width: 350px;
    height: 175px;
}

div.listBoxMoverUserControl div 
{
    height: 150px;
}

div.listBoxMoverUserControl div select
{
    width: 150px;
    height: 150px;
}

div.listBoxMoverUserControl div.listBoxMoverUserControl_column1
{
    float: left;
    width: 150px;
}

div.listBoxMoverUserControl div.listBoxMoverUserControl_column2
{
    float: left;
    width: 50px;
}

div.listBoxMoverUserControl div.listBoxMoverUserControl_column3
{
    float: left;
    width: 150px;
}@H_502_5@ 
 
我想在这个标记中的按钮居中。如何修改CSS来实现？
 
  
 
<div class="listBoxMoverUserControl">
    <div class="listBoxMoverUserControl_column1">
        <label>Test1</label>
        <asp:ListBox runat="server"></asp:ListBox>
    </div>
    <div class="listBoxMoverUserControl_column2">
        <input id="btnMoveRight" type="button" value="->" /> <br />
        <input id="btnMoveLeft" type="button" value="<-" /> <br />
    </div>
    <div class="listBoxMoverUserControl_column3">
        <label>Test2</label>
        <asp:ListBox runat="server"></asp:ListBox>
    </div>
</div>@H_502_5@