Passing Variable From Event To Page_Load?

I am thinking this is a pretty simple problem... but I can not get it to function.I just want to get the calendar control to change a date which subsequently modifies a database select statement. I can get the current code to process without error, but the variable set is always a click earlier. Of course, I want the variable to be set upon any change in the calendar control.

public partial class NewBusinessReport : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{

[code]...

Does this make sense? I just want it so that when SelectionChanged gets fired the Calendar1SelectCommandDate passes the correct date to the Page_Load page. The error I get now is:"The name 'Calendar1SelectCommandDate' does not exist in the current context"I get that the variable does not exist in the context. That actually seems to make sense based on what I have coded; however, I try to get that variable established and I still seem to be headed in the wrong direction.Basically, I have four calendar controls, one for a date (period 1 start, end and then period 2 start, end). I want to set the program so any change in that date sets off a new Select statement into the SQL server.