IF_FPM_GUIBB_LIST - Link to url in column

Hallo ,

I have a report where I list fields from table DRAD . ( Document Management )

In a column called DOKNR, I want to have an url with link to SAP std Web Dynpro: /PLMU/WDA_DIR_OIF   ..to show the Document.

In my method:  IF_FPM_GUIBB_LIST~GET_DEFINITION I have coded following:

    DATA: wa_field TYPE fpmgb_s_listfield_descr.

    CLEAR wa_field.
*  Technical field
    wa_field-name                                 = 'DOKNR'.
    wa_field-DEFAULT_DISPLAY_TYPE = 'LU'.
    wa_field-LINK_REF                          = 'TEC_FIELD_URL'.
    APPEND wa_field TO et_field_description .

I add the url to the field 'TEC_FIELD_URL' in my table, but the DOKNR column is not displayed as a "hotspot" .

What is wrong ?

Regards Rolf