Button with Icon in TableControl

Hello,

in my ModulePool I have a TableControl which contents in each line FileNames with FileExtensions.

I have created a Icon-Field in each line which displays the correct Icon (if it exists) for the FileExtension (e.g. ICON_PDF, ICON_BMP ...).

Then I created a button in each line to open the file.

What I want now is that the button changes its icon.

How can I achieve this?

In my PBO for this Dynpro I have the following code but this doesn't work:

LOOP AT gt_zdrud INTO gr_zdrud.
* FuBa zur Ermittlung der Dateierweiterung
  CALL FUNCTION 'CRM_IC_WZ_SPLIT_FILE_EXTENSION'
    EXPORTING
      iv_filename_with_ext = gr_zdrud-zzdoc
    IMPORTING
      ev_filename          = lf_filename
      ev_extension         = lf_extension.

  TRANSLATE lf_extension TO UPPER CASE.
  CASE lf_extension.
    WHEN 'PDF'. MOVE icon_pdf TO gr_zdrud-icon.
    WHEN OTHERS.
      MOVE icon_display TO gr_zdrud-icon.
  ENDCASE.

  MODIFY gt_zdrud FROM gr_zdrud.

ENDLOOP.

The table GT_ZDRUD is the table which fills the TableControl.

The field GR_ZDRUD-ICON is the field which holds the name of the icon and is defined in the dynpro as PUSH(button).