How to display the values in 0:00 format in text boxes

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C#

HTML

I want to display the values in

0:00

format in a text box. If i type 1 it should display 1:00 and characters should not allowed .

What I have tried:

<asp:TableCell>
                     <asp:TextBox ID="txtOutage" runat="server" Width="147px" Visible="true" onkeydown="return (!(event.keyCode>=65) && event.keyCode!=32);"></asp:TextBox>
                      <asp:Label ID="lblout" runat="server" Text="In Hours" ForeColor="Red"></asp:Label>
                 </asp:TableCell>