Printing format control in ALV TREE

Hello there,

I searched all over SDN but I couldn't find a solution for my problem ! It would be nice of you if you can help me sort it out.

I'm using an ALV TREE :

DATA: gv_tree TYPE REF TO cl_gui_alv_tree

CALL METHOD gv_tree->set_table_for_first_display

EXPORTING

is_hierarchy_header = gv_hierarchy_header

it_list_commentary = gv_report_title

i_save = 'A'

is_variant = gv_variant

CHANGING

it_outtab = gt_output_empty "Must be empty

it_fieldcatalog = gt_fieldcat.

I need to change printing format from X_65_255 to X_44_120.

In this method, there is no IS_PRINT to insert the new format (it exists only for GRID).

Do you have any idea?