if_bsp_model_binding~set_attribute NOT BOUND

Hello everybody,

I am novice in CRM, and I am enhancing a CRM Case:

app component     CRM-CM

view:                    CRMCMP_CMG/Detail

object type          CRM_CMG

I have to call a web service and set the results to my fields.

I have tested the WS and it IS retrieving results,  just want to assign them to my fields,

but shows MyFieldNOT_BOUND please suggest options, Thank you

method EH_ONSIGN.

DATA: l_value TYPE string.

.…

***call to external WS
…
  IF NOT TEXT IS INITIAL.
    WRITE / TEXT.
  ELSE.
*   Assign the result to variable l_value.
   CLEAR l_value.
   l_value          = out-PARAMETERS-RETURN-USER_NAME.
  ENDIF.

***end of call
***set the value to MYFIELD

   CALL METHOD me->typed_context->detail->if_bsp_model_binding~set_attribute
       EXPORTING
          attribute_path = 'MYFIELD'
          value          = l_value.

endmethod.