Custom F4 Help not getting displayed

Hello Experts,

I have the following code for  dispalying the F4 help for user.

i have this paramater on screen which should have only 3 values

AM, EC and a ' ' (i.e a blank).

  AT SELECTION-SCREEN on VALUE-REQUEST FOR groups.

  CLEAR LIST[].
  list-val  = 'AM'.
  APPEND LIST.
  CLEAR LIST.
  LIST-val  = 'EC'.
  APPEND LIST.
  CLEAR LIST.
LIST-val  = ''.
APPEND LIST.

CLEAR LIST.

  CALL FUNCTION 'F4IF_INT_TABLE_VALUE_REQUEST'
  EXPORTING
    retfield              = 'VAL'
    dynpprog              = sy-repid
    dynpnr                = sy-dynnr
    dynprofield            = 'GROUPS'
    VALUE_ORG              = 'S'
  tables
    value_tab              = LIST

    RETURN_TAB              = IT_RETURN[]

  EXCEPTIONS
    PARAMETER_ERROR        = 1
    NO_VALUES_FOUND        = 2
    OTHERS                = 3
          .

But when i run it i dont have any thing in the screen

this is what i get when i click on the button.

What could be done to fix this issue.

Abhijeet