How to avoid inserting duplicate entries into an instance

Hello All,

I’m trying to insert values into an instance which are not duplicate

<xforms:bind id="performermyfavourite" nodeset="instance('perselect1')/select1"  relevant="normalize-space(instance('favselect')/select) = 'Performer'"/>

List box

-------------------------------------------------------------------------

<xforms:select1 bind="performermyfavourite"  appearance="compact" style="height: 5em;width:15em;">

                                                            <xforms:item>

                                                                <xforms:label>Choose performer...</xforms:label>

                                                                <xforms:value/>

                                                            </xforms:item>

                                                            <xforms:itemset  nodeset="instance('performer')//Performer">

                                                                <xforms:label value="FirstName"/>

                                                                <xforms:value value="FirstName"/>

                                                            </xforms:itemset>

                                                        </xforms:select1>

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Trigger for insert values

------------------------------------------------------------------

xforms:trigger ref="instance('favselect')/addmyfav" appearance="minimal" style="vertical-align:top;">

                                                            <xforms:label><xforms:output value="concat('&lt;img src=''','/../orbeon/images/addfav.png', '''>')" mediatype="text/html"/></xforms:label>

                                                            <xforms:action ev:event="DOMActivate" if="normalize-space(instance('favselect')/select) = 'Performer'">

                                                                <xforms:insert nodeset="instance('profile')/UserProfile/MyFavorites/PerformersReference" at="last()" position="after" />

                                                                <xforms:setvalue ref="instance('profile')/UserProfile/MyFavorites/PerformersReference[last()]" value="instance('perselect1')/select1"/>

                                                            </xforms:action>

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I have tried to put the condition in action

"instance('perselect1')/select1 != instance('profile')/UserProfile/MyFavorites/PerformersReference”

To insert unique values into an instance but above condition only checks only the first node

How to avoid duplicate entries  into an instance while inserting

Orbeon version: 3.7.0beta1.200810270119

Thanks,

Srikanth A