Centering dijit.form.buttons in ContentPane

I a border container with 3 content panes. left, center, right. A left data grid (left content pane), a right data grid(right content pane), 2 buttons in the center content pane that move things from between grids .

My only problem is formatting of the buttons the buttons always appear at the top of the center content pane. I need them to be horizontally and vertically center of the center pane, regardless of browser size. My experiments have failed to center them.

<div  dojoType="dijit.layout.BorderContainer" gutters="false" >
    <div dojoType="dijit.layout.ContentPane" style="width: 45%; border: 1px solid lightgray" region="left">
        <table id="possibleChoices"
               dojoType="dojox.grid.DataGrid"
               clientSort="true"
               queryOptions="{cache:true}"
               store="possibleChoices"
               noDataMessage="<s:text name="messages.user.noChoiceAvailable"/>"
               rowsPerPage="50">
            <thead class="hideDojoLoad">
                <tr>
                    <th width="100%" field="name">possible choices</th>
                </tr>
            </thead>
        </table>
    </div>
   <div dojoType="dijit.layout.ContentPane" region="center" style="text-align: center; vertical-align: middle ">
        <button dojoType="dijit.form.Button" type="button" onclick="add"><s:text name="button.addArrow"/></button><br/>
        <button dojoType="dijit.form.Button" type="button" onclick="remove"><s:text name="button.removeA开发者_开发百科rrow"/></button>
    </div>
    <div dojoType="dijit.layout.ContentPane" style="width: 45%; border: 1px solid lightgray" region="right">
        <table id="choose"
               dojoType="dojox.grid.DataGrid"
               clientSort="true"
               queryOptions="{cache:true}"
               store="choose"
               noDataMessage="No data found"
               rowsPerPage="50">
            <thead class="hideDojoLoad">
                <tr>
                    <th width="100%" field="name">Choice Made</th>
                </tr>
            </thead>
        </table>
    </div>
</div>

Thanks to anyone that can help a beginner for any help.

the trick is putting a border container in the center content pane with an empty content pane that just takes up space.

<div  dojoType="dijit.layout.BorderContainer" gutters="false" >
    <div dojoType="dijit.layout.ContentPane" style="width: 45%; border: 1px solid lightgray" region="left">
     ....
</div>
<div dojoType="dijit.layout.ContentPane" region="center">
    <div  dojoType="dijit.layout.BorderContainer"  gutters="false" >
        <div dojoType="dijit.layout.ContentPane" region="top" style="height:40%; ">
                &nbsp;
        </div>
         <div dojoType="dijit.layout.ContentPane" region="center" style="text-align: center; ">
                <button dojoType="dijit.form.Button" type="button" onclick="add" style="vertical-align: middle"><s:text name="button.addArrow"/></button><br/>
                <button dojoType="dijit.form.Button" type="button" onclick="remove"><s:text name="button.removeArrow"/></button>
         </div>
    </div >
</div>
<div dojoType="dijit.layout.ContentPane" style="width: 45%; border: 1px solid lightgray" region="right">
           .....
</div>