I am not sure if this is what you are after but try this. It contains two user parameters asmtitle and title1.
It lists each assembly separately and as far as I can remember it displays them in the order they appear in the model tree

.breakdown
%$type %$name
%asmtitle[-30.30s]
Contains the following:
___________________________________________________________

.titles Qty;Part Number:;Title;
===========================================================
.row %$quantity[-6d];%$name[-35.35s];%title1[-35.35s]

If you have any problems let me know.

Miles addressed an answer based on the assumption that you are inquiring about the BOM report feature (Info>BOM).

My assumption is that you are inquiring about sorting of a parametric BOM TABLE on a drawing...so here goes:

In my experience, a parametric BOM table in a drawing is automatically sorted by the data in the column closest to the table origin, and the sort ascends from the origin point.  In my case, our parametric BOM table was created so that the lowermost right corner is the origin (so that it grows toward the inside of the drawing) and the rightmost column is my 'material' parameter, so that is how it sorts it.  Beyond that, it doesn't matter much to me how the table is sorted, as I use the parametric BOM balloon function that will always update as parts are added/removed.

If you have a particular variable or parameter that you would like to sort by, this could serve as valuable information, but I do not know how to remove this default sort function and replace it with another.

Recneps

Have you tried to achieve this using the filters?

Seems that filters would exclude necessary components from the BOM...how would they be used in this situation?

Recneps

Dear Friends,

Thanks for your responses.
I found out the method to do what I intended. But after getting the desired results, I found that I could not add parametric BOM balloons using that method. So the whole exercise was wasted.

Actually I wanted BOM balloons and such a sorting, both.But this is not possible in Pro/E. FILTER won't work as suggested by "helpmewithintralink". "selim" explanation is not clear to me.

For your information, I used NESTED REPEAT REGIONS to achieve the desired SORTING of assemblies and parts.

Amish Bhushan Goel

"Selim's" explanation applies to the BOM reporting feature, and devising a custom template, as enabled by config option BOM_FORMAT

Recneps