You will never be instantiating a user control by yourself. The page framework does that for you. So if you must have some property set as true during the construction, the process would be:
1. Have a public property like
2. In the aspx markup where you must have added the control do this:
<uc1:CallLogControlID="CallLogControl1" runat="server" IsCurrentCall="true"></uc1:CallLogControl>
This way this property will be set when your control is getting created.