xsl:preceding-sibling in eText Template

I am attempting to modify an eText BI Publisher template to not print duplicate headings coming from an element added via an extension.  Based upon the example data below I would only want a Header record once for DivisionCode 100 and once for DivisionCode 200 even though there are two DocumentPayable's with DivisionCode 100.  I thought I'd try sorting the data and then adding an xls:preceding-sibling check on the DivisionCode as a DISPLAY CONDITION so that it only prints when the prior DivisionCode is not equal to the current DivisionCode.  What I think I've learned is that eText templates do