There's a list of tasks. One column contains the person or people assigned to
it.
When a dataview is created, how do I create the filter at the top of the column
to show all the people listed in the list and filter by a person?
I'm working with Sharepoint Designer here's what I have so far.

<xsl:call-template name="dvt.headerfield" ddwrt:atomic="1"
xmlns:ddwrt="schemas.microsoft.com/WebParts/v2/DataView/runtime">
        <xsl:with-param name="fieldname">@Assigned</xsl:with-param>
        <xsl:with-param name="fieldtitle">Assigned To</xsl:with-param>
        <xsl:with-param name="displayname">@Assigned</xsl:with-param>
        <xsl:with-param name="sortable">1</xsl:with-param>
        <xsl:with-param name="fieldtype">x:string</xsl:with-param>
    </xsl:call-template>