I had never pressed Alt+Enter in the Preview window. But, you are right it does open up the edit window for the first field on the report. I can only open the first field. PageUp or Down does not do any thing except change the page that is viewed on multi-page reports. The first field on my report is a date field. I changed the expression from DATE() to DATE()+4 and clicked OK. It did not change the date displayed on the report. When I closed the report and previewed it again, the expression was still DATE(). So it appears as though if a user discovers the Alt+Enter key combination, they can make changes but the changes are not used or saved.