Since the variable with the multiple items is not actually multiple rows, you probably cannot use this method. I think that the letter should exist in the group footer.
You might consider including formatting in the variable within the details to handle this, something like:
stringvar MyConcat :=
numbervar TheCounter := TheCounter+1
if TheCounter/3 = int(TheCounter/3) then
MyConcat := {table.field}+replicatestring(" ",25-length({table.field})+chr(13)
else
MyConcat := {table.field}+replicatestring(" ",25-length({table.field})
So this states that the length will be 25 for each column, and to issue a carriage return after each 3rd element to give the look and feel of columnar data.
Remember to reset thecounter variable to 0 in your group header.
This should help you to cheat this, hope this helps.
-k