dynamic controls in gridview disappearng

Question

Hi guys
i am in a fix here please help.
I have a gridview which contains a dropdown list now on the selected index changed event of the drop down depending on the selected value of the drop down there are dynamically created link buttons added to the next column of the gridview in the same row as the drop down.i am able to add the link buttons but the link buttons disappear if i select from other drop down.i am also calling the function in the page load so that the buttons do not disappear.i have maintained a session to keep the track of the row index so on the bottons in the row index of session are re created & the prev buttons dis appear
How do i stop the link buttons from disappearing.