You had 1 button in the application toolbar of the selection screen, when you click that button, a pop-up window should be displayed containing 3 fields. the data to be displayed depends on the values entered by the user.

1) How to get the pop-up window? Is there any func. module is there?

2) and how to get the fields in the pop-up window? if any func. module is there , what are the parameters to be passed?
 

USE THIS fm POPUP_TO_DECIDE_INFO .

Parameters required for this FM is the Text you require to display on the popup window. 

Two buttons automatically comes on this window a Tick and a x sign if you click tick the output varaible ANSWER is J else it is A .

or 

See the below Example: 

AT SELECTION-SCREEN ON VALUE-REQUEST FOR SEL_NBA-LOW.
  PERFORM ZNEW_VALUE_HELP_NBA.

FORM ZNEW_VALUE_HELP_NBA.

  SELECT DISTINCT ZBAREA FROM ZDIVNBABU INTO TABLE ITAB_NBA.

  CALL FUNCTION 'POPUP_WITH_TABLE_DISPLAY'
       EXPORTING
            ENDPOS_COL   = 30
            ENDPOS_ROW   = 40
            STARTPOS_COL = 20
            STARTPOS_ROW = 30
            TITLETEXT    = 'Please Choose Your Entry'
       IMPORTING
            CHOISE       = COUNTS
       TABLES
            VALUETAB     = ITAB_NBA
       EXCEPTIONS
            BREAK_OFF    = 1
            OTHERS       = 2.
  IF COUNTS NE 0.
    READ TABLE ITAB_NBA INDEX COUNTS.
    SEL_NBA-LOW = ITAB_NBA-ZBAREA.
  ENDIF.
  CLEAR :ITAB_NBA,COUNTS.REFRESH:ITAB_NBA.
 

ENDFORM.                               " ZNEW_VALUE_HELP_NBA

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