[pstricks] Node and tree ?

[JBD]

Hello,

It's my first post. I have searched in the Archives but didn't find 
what I want.

How to precisely position arrows which join various elements of a tree? 
Thus, I made a tree of the type \pstree{\Tr{A}}{\Tr{B}\Tr{C}}
and wishes to connect C to B or C with A. So, it is necessary that I 
insert \rnode, but how? I tried \rnode[bl] for example, but without 
success. I manage well to obtain these arrows, but not to control by 
where they pass. Often, they go to shortest, overloading
the medium of the figure, whereas I would like that they pass round it. 
Thank you in advance for your assistance. And be lenient,
English is not my native language.

Cordially,

JBD