validator validationgroup per button

I have two date textboxes and two buttons.  CompleteButton's ValidationGroup = "Complete"  and SaveButton'ValidationGroup = "Save".
<asp:TextBox id=TextBox1 Columns="10" MaxLength="10" runat="server" /> <asp:TextBox id=TextBox2 Columns="10" MaxLength="10" runat="server" /> <asp:Button ID="CompleteButton" runat="server" Text="Complete" CssClass="button" ValidationGroup="Complete" onclick="CompleteButton_Click" /> <asp:Button ID="SaveButton" runat="server" Text="Save" onclick="SaveButton_Click" CssClass="button" ValidationGroup="Save" />
 For the 2nd TextBox, I've added 4 compareValidators, 2 for each ValidationGroup. For each ValidationGroup, one to check dataty ...