SharePoint UserField control - any way to limit selection in people dialog?

I'm using the SharePointWebControls UserField control. I know that if I use the PeopleEditor, I can limit the user selection to those in a single SharePoint group by using SharePointGroup="groupname". But for various reasons, I cannot use the PeopleEditor here.

Is there similar functionality for the UserField that I'm just not finding? I'm using SharePoint 2010, bt开发者_StackOverflow中文版w, but I doubt that that matters...

Thanks in advance...

UserSelectionScope

Optional Integer. Specifies a scope for selecting user names in a user field on an item form. If the value is 0, there is no restriction to a SharePoint group. If the value is greater than 0, user selection is restricted to members of the SharePoint group whose ID equals the value that is specified.

Specify this in your Field definition. Taken from:

http://msdn.microsoft.com/en-us/library/aa979575.aspx