In table control internal table records are duplicated

hi all,

I am developing the table control in the module pool.

Table control has 5 fields;

sr_no   roll_no   pan_details   city   country   age   division

here in roll_no(serach help provided) when i select roll no and press enter button the following fields pan_details , city ,country are populated automatically.

and after populating the user is manually entering the age and division.

Then the user is supposed to press save button.

after pressing save button the internal table is automatically modifying 2 times.  1st---when i press enter and 2----when i press save.

so my internal table now having 2 records which are same

but my requirement is the internal table should be modified only once i.e after i press save button and should contain only 1 record. 

please guide me where to write the code so that internal table does not get modified two times.