I would venture the reason you have received no responses is the lack of context, really going to need QVW file with the information provided, as I am not sure how else you expected anyone to know what was wrong with the expression... Most people are not going to make assumptions etc., so you must include enough information in order for them to be able to research what you are trying to do to sort out why it is not working as you wish.
The best I can do as a point in the right direction is the following Design Blog post and I will include the base URL last in case you wish to search further yourself.
To help users find verified answers, please do not forget to use the "Accept as Solution" button on any post(s) that helped you resolve your problem or question. I now work a compressed schedule, Tuesday, Wednesday and Thursday, so those will be the days I will reply to any follow-up posts.
