Hi Hilary, thanks for your answer, now I understood the method: binding and conditional formatting.
However I got a design/layout problem, this has occured me before and now with also this: Even though the rule "hide this control" applies; infopath doesn't completely hide the control but instead leaves it's borders visible. This results in a thin line (or space, if transparent borders) to the form. How do I get rid of those thin lines? Another problem is that even though I have a table (1x1) and hide the section that is in it (and made sure they are no space between section and table borders), still the table gives me blank row. Where can this blank row possible still come from??