Prevent tab to next field if current field is invalid

I have a form with some required data. One of the requirements is to prevent the user from tabbing to the next field if the current field they are in is invalid. Here is a simple form...
Field 1: <asp:textbox ID="Textbox1" runat="server"></asp:textbox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" ControlToValidate="Textbox1" runat="server" ErrorMessage="RequiredFieldValidator">*</asp:RequiredFieldValidator>
<br />
Field 2: <asp:textbox ID="Textbox2" runat="server"></asp:textbox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator2" ControlToValidate="Textbox2" runat="server" ErrorMessage="RequiredFieldValidator">*</asp:RequiredFieldValidator>
<br />
<asp:button ID="Button1" runat="server" text="Button" />
So if the ...