How can I add and access a custom attribute to a user control?

I am trying to add a custom attribute to a custom user control (ASCX file); can this be done?

I would like my user control tag to look something like this:
<uc:WebUserControl ID="WebUserControl1" runat="server" CustomAttr="value" />I would like to then access the value of CustomAttr from the codebehind during Page_Load.Am I barking up the wrong tree here?  ...