for clarity sake, if you are placing a field in the report header and report footer, all crystal does is display the value from the first row of data (header)and the last row of data (footer) in your total data set. If you change the sort order it will change what appears in because it changes what becomes the first and last rows of the data set.
As lockwelle suggests if you group by program name this will also change the sort order (sorting on groupname first) and will therefore impact first and last rows.