Hello Bruno,
eventually I was able to solve my issue, by coding the message like described in the below Forum
http://scn.sap.com/community/crm/webclient-ui-framework/blog/2013/05/21/pass-variables-to-long-text
Now whenever the user try to enter a double entry by saving the following message is going to be raised. See the Image below:
The final code that the implementation of the BADI CRM_BP_UIU_SAVE is employing is the following:
lv_collection
= gv_access_header->get_related_entities( iv_relation_name = 'ZEXT_BOL_RELAT00000E' ).
IF lv_collection IS BOUND AND lv_collection->size( ) > 0.
lv_iterator = lv_collection->get_iterator( ).
lr_relation2 ?= lv_iterator->get_first( ).
WHILE lr_relation2 IS BOUND.
lr_relation2->get_properties( importing ES_ATTRIBUTES = ls_fore ).
LV_JAHR = ls_fore-ZZFLD00001O.
READ TABLE lt_fore with key ZZFLD00001O = lv_jahr transporting no fields.
IF sy-subrc is not initial.
append ls_fore to lt_fore.
LV_LOBOUT = ls_fore-ZZFLD00001S.
LV_LOBCON = ls_fore-ZZFLD00001T.
LV_LOBSYS = ls_fore-ZZFLD00001U.
LV_LOBSUM = LV_LOBOUT + LV_LOBCON + LV_LOBSYS.
lr_relation2->SET_PROPERTY( IV_ATTR_NAME = 'ZZFLD00001V'
IV_VALUE = LV_LOBSUM ).
lr_relation2 ?= lv_iterator->get_next( ).
ELSEIF sy-subrc is initial.
lo_core = cl_crm_bol_core=>get_instance( ).
lr_message_cont = lo_core->get_global_message_cont( ).
lr_message_cont->add_message( iv_msg_type = 'E'
iv_msg_id = 'ZTDS_INFO'
iv_msg_number = '004'
iv_msg_v1 = LV_JAHR
iv_show_only_once = abap_true ).
EXIT.
ENDIF.
ENDWHILE.
ENDIF.
lo_core = cl_crm_bol_core=>get_instance( ).
lo_core->modify( ).
Reason why I am going to close this discussion.
Many thanks for all the Support and best regards.
Andrea