How to limit path field selection only to one level?

Hi

Requirement:

      I have a pathfield where i have set a root path

for eg: /content/geometrix

author shud be able to select only among these nodes. he shud not be able to select the child nodes of each individual nodes

eg: he can select /content/geometrixx/English

but he shud not select child page of English

ie : /content/geometrixx/English/Toolbar shud not be assesible to him

Hope my requirement is clear. Is there anyway we can achieve this.. If we can limit the nodes from expanding; then it would be very useful . Is there any way we can achieve this??

Thanks

Veena