BaCK button.PAI

hi experts ,

i have two table control in two different screen.suppose i am entering some value in screen A with some amount , two to three line i enter.

when i press Enter key and Click on BACK (PAI) button i am getting corresponding sum of all field in Table control of Screen B . ITs working fine.

Now my quation that

If i never press Enter key and dirctly clicking on Back (PAI) button then corresponding sum is not reflecting in second table control of B screen.

How to solve above problem..

Point is assured.