RadioButtonList and TextBox as one option

Hello, I need to have this radio button list:
- 4:3
- 16:9
- other, please specify: [TextBox]
I don't mind do I use Web controls or HTML controls...
Since RadioButtonList doesn't allow text fields nor TextBox to be nested in ListItem,
I tried with several HTML controls, but how do I fetch their values?
I have:
<label><input type="radio" name="screensize" id="screensize_0" runat="server" value="4:3" />4:3</label> <label><input type="radio" name="screensize" id="screensize_1" runat="server" value="16:9" />16:9</label> <label><input type="radio" name="screensize" id="screensize_2" runat="server" value="" />other: <input type="text" id="screensize_2_text" runat="server" ...