How to display an image depending on an intance data value

Hi all,
 
I have a model that looks like this :
 <xforms:model id="model_wsrp_rewrite_" schema="resource/schema/schemadt.xsd">
            <xforms:instance id="data_wsrp_rewrite_"
                nweb:pageflow-replace-data="always" nweb:primary-input-data="true">
                <data xmlns="">
                    <record>
                          ...
                          <projectstatus>green</projectstatus>
                          ...
                     </record>
                 </data>
            </xforms:instance>
        </xforms:model>
 
Dependiing on the value of projectstatus, I want to display an image :
if projectstatus = "green", the image source is "images/green.gif"
if projectstatus = "red", the image source is "images/red.gif"
 
How can I do that in xFroms ?
Thanks in advance,
 
Catherine