Set radio the first time a date is entered

form.xml

<xh:html xmlns:xh="http://www.w3.org/1999/xhtml" xmlns:xf="http://www.w3.org/2002/xforms"
         xmlns:xs="http://www.w3.org/2001/XMLSchema"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns:ev="http://www.w3.org/2001/xml-events"
         xmlns:xi="http://www.w3.org/2001/XInclude"
         xmlns:xxi="http://orbeon.org/oxf/xml/xinclude"
         xmlns:xxf="http://orbeon.org/oxf/xml/xforms"
         xmlns:exf="http://www.exforms.org/exf/1-0"
         xmlns:fr="http://orbeon.org/oxf/xml/form-runner"
         xmlns:saxon="http://saxon.sf.net/"
         xmlns:sql="http://orbeon.org/oxf/xml/sql"
         xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"
         xmlns:fb="http://orbeon.org/oxf/xml/form-builder">
    <xh:head>
        <xh:title>Untitled Form</xh:title>
        <xf:model id="fr-form-model" xxf:expose-xpath-types="true">

            <xf:action event="xforms-value-changed" observer="dob-control">
                <xf:var name="binding" value="xxf:binding('dob-control')"/>
                <xf:action if="empty($binding/@changed[. = 'true']) and $binding castable as xs:date">
                    <xf:setvalue if="xs:date($binding) + xs:yearMonthDuration('P25Y') &lt;= current-date()"
                                 ref="xxf:binding('ncb-control')">true</xf:setvalue>
                    <xf:delete ref="$binding/@changed"/>
                    <xf:insert context="$binding" origin="xxf:attribute('changed', 'true')"/>
                </xf:action>
            </xf:action>
            
            <!-- Main instance -->
            <xf:instance id="fr-form-instance" xxf:exclude-result-prefixes="#all" xxf:index="id">
                <form>
                    <section-1>
                        <dob/>
                        <ncb>false</ncb>
                    </section-1>
                </form>
            </xf:instance>

            <!-- Bindings -->
            <xf:bind id="fr-form-binds" ref="instance('fr-form-instance')">
                <xf:bind id="section-1-bind" name="section-1" ref="section-1">
                    <xf:bind id="dob-bind" name="dob" ref="dob" xxf:whitespace="trim" type="xf:date"/>
                    <xf:bind id="ncb-bind" ref="ncb" name="ncb" type="xf:boolean"/>
                </xf:bind>
            </xf:bind>

            <!-- Metadata -->
            <xf:instance xxf:readonly="true" id="fr-form-metadata" xxf:exclude-result-prefixes="#all">
                <metadata>
                    <application-name>a</application-name>
                    <form-name>a</form-name>
                    <title xml:lang="en">Untitled Form</title>
                    <description xml:lang="en"/>
                </metadata>
            </xf:instance>

            <!-- Attachments -->
            <xf:instance id="fr-form-attachments" xxf:exclude-result-prefixes="#all">
                <attachments>
                    <css mediatype="text/css" filename="" size=""/>
                    <pdf mediatype="application/pdf" filename="" size=""/>
                </attachments>
            </xf:instance>

            <!-- All form resources -->
            <xf:instance xxf:readonly="true" id="fr-form-resources" xxf:exclude-result-prefixes="#all">
                <resources>
                    <resource xml:lang="en">
                        <section-1>
                            <label>Untitled Section</label>
                        </section-1>
                        <dob>
                            <label>DOB</label>
                            <hint/>
                            
                        </dob>
                        <ncb>
                            <label>Protection NCB</label>
                            <hint/>
                        </ncb>
                    </resource>
                </resources>
            </xf:instance>

            <!-- Utility instances for services -->
            <xf:instance id="fr-service-request-instance" xxf:exclude-result-prefixes="#all">
                <request/>
            </xf:instance>

            <xf:instance id="fr-service-response-instance" xxf:exclude-result-prefixes="#all">
                <response/>
            </xf:instance>

        </xf:model>
    </xh:head>
    <xh:body>
        <fr:view>
            <fr:body xmlns:p="http://www.orbeon.com/oxf/pipeline"
                     xmlns:oxf="http://www.orbeon.com/oxf/processors"
                     xmlns:xbl="http://www.w3.org/ns/xbl">
                <fr:section id="section-1-control" bind="section-1-bind">
                    <xf:label ref="$form-resources/section-1/label"/>
                    <fr:grid>
                        <xh:tr>
                            <xh:td>
                                <xf:input id="dob-control" bind="dob-bind">
                                    <xf:label ref="$form-resources/dob/label"/>
                                    <xf:hint ref="$form-resources/dob/hint"/>
                                    <xf:alert ref="$fr-resources/detail/labels/alert"/>
                                    
                                </xf:input>
                            </xh:td>
                            <xh:td>
                                <fr:yesno-input xmlns="http://orbeon.org/oxf/xml/form-builder"
                                                xmlns:xxbl="http://orbeon.org/oxf/xml/xbl"
                                                id="ncb-control"
                                                bind="ncb-bind">
                                    <xf:label ref="$form-resources/ncb/label"/>
                                    <xf:hint ref="$form-resources/ncb/hint"/>
                                    <xf:alert ref="$fr-resources/detail/labels/alert"/>
                        
                        
                                </fr:yesno-input>
                            </xh:td>
                        </xh:tr>
                    </fr:grid>
                </fr:section>
            </fr:body>
        </fr:view>
    </xh:body>
</xh:html>