Dynamic Template control and value persistence

Question

Hi friends
I have created a gridview using ITemplate to generate textboxes in cells and to display the data. The grid is bound using a datatable in PreRender event.
On Page refresh the modified value gets replaced by the existing value from datatable. If I do not bind the gridview in each refresh, the textboxes  gets vanish from the gridview.
Can any one help me to overcome this problem.
Does viewstate will have any role in this?
Thanks in advance