Unable to find a ComboBox component for that would work in an Ext Grid, permit multiple selections, and support both local and remote datasources with multiple fields (one for display, one for the index), I set out to build my own some time back.
Note:Here is an example of the MultiSelect ComboBox.
REXML could not parse this XML/HTML:
<p>
<table>
<tr>
<th><div id="menu" style="text-align:left;"></div><th>
<td><input type="button" value="Show Selected" onclick="alert('Currently Selected States: ' + menu1.getValue() );"></td>
</tr>REXML could not parse this XML/HTML: </table>
REXML could not parse this XML/HTML: </p>
Here is an example of the MultiSelect menu working in an Ext JS Grid.
The source below above is pretty self explanatory, feel free to post in the ExtJS forums with any questions as I will lurk there.
Here is the javascript used to create the example above: