Dropdown in datalists

Hi,

I have a datalist that contains a series of thumbnails. I am
in the process of paging this datalist so that only 20 images
are displayed at a time. Each image has associated with
it a pair of dropdown boxes. The user selects theor choices
from the dropdown boxes and then moves to the next
series of 20 images. The postbackURL of the button
click contains the information regarding the next page to
display.

Now, I want to be able to capture the users selections
from the dropdown boxes associated with each thumbnail
before the next page of thumbnails is bound to the datalist
and then bind the next set of records from the datasource
to the datalist.

Does anyone have any ideas which event I should write
my code in to determine which dropdown boxes have had
their values changed before the databinding of the next
images occurs?

Many thanks,

Jason.
.