if you're using a djFilteringSelect, yes, you should be able to add something like this as a child of the djFilteringSelect:

<xp:selectItems>

<xp:this.value><![CDATA[#{javascript:var list = ["one","two","three","four"]; list[list.length] = "five"; return list;}]]></xp:this.value>

</xp:selectItems>

 

Return the a list or java.util.Vector in the this.value tag, computing as you wish, separate labels and values with a |, if you use labels. 

 

Rich