Richard, a question for you... Am I reading your question right, are you using Jaspersoft Studio with ReportServer (reportserver.net)? If so, do you have it connected to upload the JRXML files directly from Studio?
I'm writing some reports to highlight all fields with missing data in yellow. There can be 10-20 fields on any one of these reports. I have the condition expression figured out for a specific field ($F{fieldName} == null), but want to somehow wildcard the field's name so that I can simply apply the style to any field I want evaluated. Otherwise, I have to create a conditional style specifically for each field.