pro get_user_blocks,start_block,end_block
common block,sblock,eblock

init_sblock = start_block
init_eblock = end_block

;  create a GUI base

   tbase = WIDGET_BASE(/column,TITLE="Specify block range")

;  create the label and text fields

   prompt1 = "Specify start and end block numbers for area of interest"
   prompt2 = "(Start and end blocks for the file are shown as initial values)"
   label1 = WIDGET_LABEL(tbase,VALUE=prompt1,/ALIGN_CENTER,UNAME="label1")
   label2 = WIDGET_LABEL(tbase,VALUE=prompt2,/ALIGN_CENTER,UNAME="label2")
   sbtext = CW_FIELD(tbase,TITLE="Start block:",VALUE=start_block,$
              /INTEGER,UNAME="stblock")
   ebtext = CW_FIELD(tbase,TITLE="End block:",VALUE=end_block,$
              /INTEGER,UNAME="endblock")
;  create  DONE and RESET buttons
   bbase = WIDGET_BASE(tbase,/ROW,/ALIGN_CENTER)
   reset = WIDGET_BUTTON(bbase,value="RESET",UVALUE="reset",UNAME="reset")
   done = WIDGET_BUTTON(bbase,value="DONE",UVALUE="done",UNAME="done")

   WIDGET_CONTROL,tbase,/REALIZE
   WIDGET_CONTROL,tbase,SET_UVALUE=[sbtext,ebtext,init_sblock,init_eblock]

   XMANAGER,'get_user_blocks',tbase
   start_block = sblock
   end_block = eblock
end