Client side

YUIAsp.Net Calendar allows you to call a custom javascript handler when the user selects/deselects a date.

		<yui:Calendar ID="Calendar1" OnClientSelect="OnCheckHandler" OnClientUnselect="OnUncheckHandler"
        runat="server" AllowMultiSelect="true" />
	

OnClientSelect is called when the user selects a date.

		function OnCheckHandler(sender, args) {
        alert("checked " + args.date);
    }
	

OnClientUnselect is called when the user selects a date.

		function OnUncheckHandler(sender, args) {
        alert("unchecked " + args.date);
    }