Forms Data Controls :: Date Text Cell In Gridview Needs Validating

I have the following piece of code which I was hoping would result in an error message being displayed if an incorrect date format was input rather than an website error page saying "The string was not recognized as a valid DateTime."

<asp:TemplateField HeaderText="DateCompleted" SortExpression="DateCompleted"> <EditItemTemplate> <asp:TextBox ID="TextBox2" runat="server" Text='<%# Bind("DateCompleted") %>'> </asp:TextBox> <asp:CompareValidator ID="CompareValidator" ValidationGroup="GridView1" ControlToValidate="TextBox2" errormessage="Invalid Date" Display="Dynamic" Operator="DataTypeCheck" Type="Date" runat="Server" /> </EditItemTemplate> <ItemTemplate> <asp:Label ID="Label2" runat="server" Text='<%# Bind("DateCompleted") %>'></asp:Label> </ItemTemplate> </asp:TemplateField>