you can get some Idea From This code...and change it according to your requirement..to implement this u need a Latest Version 4.0 of Ajax control Toolkit
this is the .aspx page
<body>
<form id="form1" runat="server">
<asp:scriptmanager id="ScriptManager1" runat="server" xmlns:asp="#unknown">
</asp:scriptmanager>
<table>
<tr> <td> From Date</td>
<td> <asp:textbox id="TextBox1" runat="server" xmlns:asp="#unknown"></asp:textbox>
<asp:calendarextender id="CalendarExtender1" runat="server" xmlns:asp="#unknown">
Enabled="True" TargetControlID="TextBox1" Format="dd/MM/yyyy">
</asp:calendarextender>
</td>
</tr>
<tr><td>To Date</td>
<td> <asp:textbox id="TextBox2" xmlns:asp="#unknown">
runat="server"></asp:textbox>
<asp:calendarextender id="CalendarExtender2" runat="server" xmlns:asp="#unknown">
Enabled="True" TargetControlID="TextBox2" Format="dd/MM/yyyy"></asp:calendarextender>
</td> </tr> </table>
</form>
</body>
and simply add this code on page load the .cs file is
protected void Page_Load(object sender, EventArgs e)
{
CalendarExtender1.StartDate = DateTime.Now;
CalendarExtender2.StartDate = DateTime.Now.AddMonths(1);
}
In the above example First calender start with current date and second calender start after one month from current date..
i hope this will give you a some hint
thanks