FM for Drop down in a field

CALL FUNCTION 'VRM_SET_VALUES'
    EXPORTING
      ID              = P_L_ID “Field name
      VALUES          = P_L_T_VALUES “All the values key and TEXT
    EXCEPTIONS
      ID_ILLEGAL_NAME = 1
      OTHERS          = 2.
  IF SY-SUBRC <> 0.
    MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
            WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
  ENDIF.

FM show message log

CALL FUNCTION 'MESSAGES_INITIALIZE'.
  CLEAR :L_R_RETURN,P_G_F_ERROR.
  LOOP AT P_G_T_RETURN  INTO L_R_RETURN .
    CALL FUNCTION 'MESSAGE_STORE'
      EXPORTING
        ARBGB = L_R_RETURN-ID
        MSGTY = L_R_RETURN-TYPE
        TXTNR = L_R_RETURN-NUMBER
        MSGV1 = L_R_RETURN-MESSAGE_V1
        MSGV2 = L_R_RETURN-MESSAGE_V2
        MSGV3 = L_R_RETURN-MESSAGE_V3
        MSGV4 = L_R_RETURN-MESSAGE_V4
        ZEILE = L_R_RETURN-ROW.
  ENDLOOP.
  IF P_G_F_ERROR EQ G_C_X.
    CALL FUNCTION 'MESSAGES_SHOW'.
  ENDIF.
  CALL FUNCTION 'MESSAGES_INITIALIZE'.

FM get the project details

CALL FUNCTION 'BAPI_PS_INITIALIZATION'.

  CALL FUNCTION 'BAPI_BUS2001_GETDATA'
    EXPORTING
      I_PROJECT_DEFINITION = G_F_PROJECT_DEFINITION
    IMPORTING
      E_PROJECT_DEFINITION = G_R_PROJECT_DEFINITION
    TABLES
      ET_RETURN            = L_T_RETURN2.

  CLEAR G_F_ERROR.
  LOOP AT L_T_RETURN2 INTO G_R_RETURN."Error Type A E or X .
    IF G_R_RETURN-TYPE CA G_C_AEX.
      G_F_ERROR = G_C_X.
    ENDIF.
  ENDLOOP.

Get the WBS status (user and system status)

*-- Initialization of BAPIs 

CALL FUNCTION 'BAPI_PS_INITIALIZATION'.

  CALL FUNCTION 'BAPI_BUS2054_GET_STATUS'
    IMPORTING
      RETURN         = G_R_RETURN1
    TABLES
      I_WBS_ELEMENTS = G_T_WBS_ELEMENTS
      E_USER_STATUS  = P_G_T_USER_STATUS.

  CLEAR G_F_ERROR.
  IF G_R_RETURN1-TYPE CA G_C_AEX."Error Type A E or X .
    G_F_ERROR = G_C_X.
  ENDIF.