validations in user control

Hello all,
          I've an application where in i'm using same user control for different functionalities.
The user control has 2 textboxes ..  i need to validate them on button control in respective parent pages.
 my application looks like this:
Parent page with button and  a user control(which has 2 textboxes).
I need to validate the textboxes in button event of parent page
User Control:
<asp:TextBox ID="txtSubject" Width="90%" CssClass="TextBoxStyle" runat="server"></asp:TextBox> <asp:RequiredFieldValidator ID="SubjectRequired" runat="server" ControlToValidate="txtSubject" ErrorMessage="Subject is required." ToolTip="Subject is required." ValidationGroup="Compose" ...