Dynamic controls ,ViewState and close button

Hi,
I'm creating a dynamic filter for a gridview by using three usercontrols One for datetime,one for numerinc and one for string
every user control contains label which hold the column name of the gridview, dropdownlist which contains the operation that the user can do and one or two textboxes(numeric at  UC1, string textboxs at UC2, datetime textboxes at UC3) and depending on the operation that the user chose I show or hide the second textbox
example the user chose between from the drop down list I show the second textbox (by javascript)
CarNumber Between | 10 | |20|
SellDate biggerthan 2/2/2000
I use the view state to save the user changes and I create from the user inputs at the server the gridview sortexpression
By reading the usercontrols containts.
SORTEXPERTION ="(CarNumber Between 10 and 20) and (SellDat > #2/2/2000)"
No I want to ...