Changing the Format of Summary Bars in P6

Hi, I've got a problem that hopefully someone can help me with.  I have created a programme that has several activity codes allocated to each of the tasks, to enable me to group them in different ways (rather than just using a WBS).  Most of the time this programme will be viewed while summarised, so the tasks will not be seen, just the summary bars. 

I don't want P6 to show the bar based upon the code value, as all of my tasks have a value for each code, and it's not the actual code value that matters.  I'd like to change to bar style for the "level", or Grouping Band when I view the programme Grouped and Sorted by the activity codes.

So, for example, if I've got 4 Activity Codes (Code 1 to 4), each with 4 Code Values (Value A to D), the layout (collapsed to the lowest level so I don't see the actual tasks, but see all of the summaries) is:

(I've used a different format and indent for each "level"):

Code 1: A

   Code 2: A

    Code 3: B

      Code 4: C

      Code 4: D

  Code 2: B

    Code 3: C

      Code 4: A

      Code 4: B

    Code 3: D

      Code 4: B

      Code 4: C

Code 1: B

  Code 2: A

    Code 3: C

      Code 4: A

The problem I've got is that whatever I do, the summary bar shown for each of these "levels" look the same.

Thanks all,

Jimbo.