Call screen and save text from ALV Report

Hi genius,

   I have one alv report .

  this alv report print MATNR ERSDA.

while clicking the MATNR , to call the new screen for user enter the text. this test should be store against the matnr.

how to done this scenario.

this is my coding...

form user_command using ucomm     type  sy-ucomm
                                        selfield     type  slis_selfield.

   data : temp_val type mara-matnr.

   case ucomm.
         when '&IC1'.
                      if selfield-fieldname eq 'MATNR'.
                         temp_val = selfield-value.
                         call screen '0101'.
                      endif.
    endcase.
endform.

in my screen ' 0101' , i have create input/output button.

        1.  when am clicking the matnr , my screen not appear.

.