Trim does not remove blank fields. Trim removes SPACES around data.
If you don't want blank fields to show up you can set the Can Shrink property of the control to YES and you also need to set the Can Shrink property of the section it is in to YES. Now it won't shrink if there are labels next to the text boxes as those don't have the ability to shrink.
See if that works for you and if not, post back and we'll dig further.