Adding a list on design time to the Html Editor

[Lior]

Hi all,

i've created a new server control named: NewLabel that inherit from
Label control.
I add a new attribute from this control named "Permission" and i
created a "tag prefix" in the
..config file to this new control.
when i add this control it works fine and the intellisense give me the
prefix and the new attibute
that i added to this control.
example:
<NewLabel:NewLabel ID="l1" runat="server" Permission=

</NewLabel:NewLabel>

the problem is that i don't know i to add the functionality that when i
type the permission
attribute a list will be opend to me (like: "User", "Admin"...) like
when you type "runat=" and
then you get a list and you can chose "server" from it and the develper
doesn't need to
get what are his options.
i'm working on vs2005!!!, in 2003 it was easy to change the asp.xsd
file.
how do i solve this?

thanks!!!