Hi greendean,
You don't need either bookmarks or cross-references for this. Instead, if you apply a unique character Style or paragraph Style to the data (which you might solicit via a content control, you can have it appear in the header via a STYLEREF field that references the Style. See:
http://office.microsoft.com/en-us/wo...005186193.aspx
http://wordfaqs.mvps.org/StyleRef.htm