As I am so new to XSL it took a while to figure this out.
Here's the line I modified in the Advanced Table:
<
xsl:variable name="filteredData" select="udt:Data[udt:Active_UDT_Original='true' and (contains(*[name()=$searchColumns][1],$search) or contains(*[name()=$searchColumns][2],$search) or contains(*[name()=$searchColumns][3],$search) or contains(*[name()=$searchColumns][4],$search) or contains(*[name()=$searchColumns][5],$search)or contains(*[name()=$searchColumns][6],$search)or contains(*[name()=$searchColumns][7],$search)or contains(*[name()=$searchColumns][8],$search)or contains(*[name()=$searchColumns][9],$search)or contains(*[name()=$searchColumns][10],$search))]" />
I inserted "udt:Active_UDT_Original='true' and" in front of the section that sets up the sorting and enclosed the sorting section in an additional set of ().
Now I can filter the Advanced Table and get everything I need... Searching, Detail, Sorting and Paging, on only the "Active" items. (active is a check box, hence the "_UDT_Original='true'", for those of you new to this as I am.
Thanks for your patience.