you got me...you want a value, from what amounts to a future line, to be displayed in the current line. You might try calling the subreport using the value from the 'NEXT()' field, but no guarentees.
This is kind of a thorny quandry. I would bring out the next value in a new column in the result set (I use stored procs and can accomplish this...I think, but it probably won't be easy/pretty). Crystal, and just about every reporting system out there, is set up to deal with values in the this row of the data, so pointing to another row in the data is an iffy proposition and may not be doable.