Problem with module pool

Hi All,

i am working on a table contol in module pool programming.

Now i have three columns in my control table.

In my user_command_0100 input, i have written these code,

so that when user hits enter, he will get two fields filled in table control.

MODULE USER_COMMAND_9000 INPUT.

WHEN 'ENTER'.
       PERFORM DISP_DATA.

Now, inside FORM disp_data. i am selecting two fields from a table.

FORM DISP_DATA .
SELECT MANDT FIELD1 FIELD2
     FROM ZTABLE
     INTO  TABLE  IT_FINAL.
  ENDFORM.  

Now the problem is that, when user hits first enter , the two fields gets filled in my table control.

But the third filled will be filled by user on runtime.

So, the problem is that, when user fills the third field and again hits enter, the value entered by him gets disappeared.

Because it again initialize only two fields, but my requirement is when user fills third field value at run time,

it should retain in table control.

Please tell me what changes i have to perform, in the above code.