javascript do post back method?

Hi...!

i have two text fields in form..

(category code and category name)..

i am passing the values of that two fields  from grid to text fields for update purpose.....

the values passed to text fields..

but when i am click update button . only error message displayed.. modification not done(Error message is "no values in text fields to modify)

.....

i heard the do post back method in javascript to update this kind of application.

So help in that javascript do post back method to solve this issue..