In Design, the report structure would be something like this:
-------------------
Person Group Header
-------------------
Year Group Header
-------------------
Detail Band
-------------------
Year Group Footer
-------------------
Person Group Footer
-------------------
You'll need, at most, three different formulas to pull this off. Here is a run down of what each one would be and how they would look.
"PreAugHolder" (Used to hold onto last year's august info.)
shared stringvar PreAug:=DU
//"DU" is a placeholder and should be replaced with the that DU string variable you referred to in your post.
"PreAug" (Used to display last Aug)
shared stringvar PreAug;
PreAug;
"Sweeper" (Used only if you are running multiple people in one report to clear shared variables between the different people)
shared stringvar PreAug:="";
Now you just need to place them in the correct location and supress the right bands. This is what your design view would look like after placing these new formulas.
-------------------
Person Group Header @Sweeper <--(Supress)
-------------------
Year Group Header
-------------------
Detail Band @PreAug
-------------------
Year Group Footer <--(Supress) @PreAugHolder
-------------------
Person Group Footer
-------------------
If you follow what I've done, the Detail Band will show the last detail band's "DU" which equates to last year's August "DU" since we are grouping by Year. Right next to it you could drop your August "DU" string to display the current year's August "DU".
The report then rolls down to the the Year Group Footer and stores that current year's "DU" to be used in the next record.
Finally, when you've run all the details you need for that person and crystal rolls on to the next person, the stored "DU" information from your last person is swept clean by the "Sweeper" formula.
I hope this helps.