Method 1

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a) Create a subscreen area in your screen layout where you want to create the select options.

b) In the top include of  your module pool program declare a selection screen as a subscreen e.g.

       SELECTION-SCREEN BEGIN OF SCREEN 100 AS SUBSCREEN.

             select-options s_matnr for mara-matnr.

       SELECTION-SCREEN END OF SCREEN.

c) In the PBO and PAI of the main screen where the select options needs to be created do a call subscreen of the above screen (100).

       CALL SUBCREEN sub_area INCLUDING    

  This call subscreen statement is necessary for transport of values between screen and program.

Note: All validations of the selection screen fields e.g. the s_matnr field created above should be done in selection screen events like AT SELECTION-SCREEN etc and not in PAI. These selection screen validations etc should be done in the top include only.

Method 2

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a) Create 2 separate fields in your screen layout - one for the low value and one for the high value. Insert an icon beside the high value which will call the multiple selections popup screen on user command. Use function module COMPLEX_SELECTIONS_DIALOG to achieve this. 

struc_tab_and_field-fieldname   = con_cust.      " 'KUNNR'

struc_tab_and_field-tablename = con_kna1.     " 'KNA1'.

CALL FUNCTION 'COMPLEX_SELECTIONS_DIALOG'

          EXPORTING

*           TITLE                   = ' '

            text                         = g_titl1                                " 'Customers'

            tab_and_field     = struc_tab_and_field

          TABLES

            RANGE                   = rng_kunnr

          EXCEPTIONS

            NO_RANGE_TAB          = 1

            CANCELLED                    = 2

            INTERNAL_ERROR     = 3

            INVALID_FIELDNAME = 4

            OTHERS                           = 5.

IF NOT rng_kunnr[] IS INITIAL.

*          Read the very first entry of the range table and pass it to

*          dynpro screen field

           READ TABLE rng_kunnr INDEX 1.

           IF sy-subrc = 0.

              g_cust = rng_kunnr-low.

           ENDIF.

You can use the return table rng_kunnr to populate your own internal range table with the values entered by the user. Basically here you are just simulating the work of a select-options parameter by module pool screen elements.