DataBind OnSelecting and ReInit Page variables

Hi,
I have a problem with page private variables (but it also arises with
controls in the page).
The page is a Search Page with 2 textboxes and a search button with a
repeater to show
the results.
The repeater is bound on an objectDataSource.
On the OnClick event handler I set an Int32 variable inside the page
then I call the DataBind
on the repeater.
The strange thing is when I step into the OnSelecting handler of the
objectDataSource.
I need the Integer value to pass as an InputParameter to the
SelectMethod and the value
is always 0... It seems like the Page object is reinitialized.
Then, If I step into a subsequent event handler, as PageUnload, the
variable has the correct
value...
Can someone help me to discover how it can happen ?

Thanks a lot,
Edoardo