accessing a control in a nested user control

I have a user control that contains another user control in my page. So it looks like this:

myPage.aspx <- uc1.ascx <- uc2.ascx

uc2.ascx has a simple RequiredFieldValidator, which looks like this:
<asp:TextBox ID="tb" runat="server" />
<asp:RequiredFieldValidator ID="rfv" runat="server" ControlToValidate="tb" /> I need to get the rfv control in uc2.aspx from myPage.aspx.
This would be easy if that rfv were in uc1.ascx, which I could do this:
BaseValidator revFound = (BaseValidator)this.uc1.FindC ...