Actitvity search view - picklist that acts like multypicklist

[LapiShai]

Hi experts

I am a developer on an S4HANA system CM module on WEBUI

The request was to add a selection field to the activity search BT126S_APPT
I added a new selection field to my screen and the selection works great
I wrote the get_V method in the controllers vlass (IMPL) and it gets all the wanted values
And I have two problems with it:

1. The field acts like multypicklist when I want it to be a regular picklist - I tried doing it by writing the get_p method but it seems like it doesn't get to it at all (In Debug mode it didn't stop there with the field type parameter)

2. I can't catch the event when user picks a value. and there is no round trip

This is the coding in get_v method:

  SELECT *
  FROM zcodegroup_shlp_source
  INTO TABLE @DATA(lt_codegroups).

  LOOP AT lt_codegroups ASSIGNING FIELD-SYMBOL(<ls_ddlb>).
    INSERT VALUE #( key = <ls_ddlb>-codegruppe value = <ls_ddlb>-code_value ) INTO TABLE cs_result-ddlb_options.
  ENDLOOP.

  cs_result-server_event = 'ZZDUMMY'.

Thanks in advance
Shai Lapidot