Classification tree data structure

Hi there,

I am growing classification trees using the 'tree' package add-on to R.

I would like to convert the 'R' output to the SAS format used by Salford Systems' commercial CART software in order to interface with some 
other software.

My question is:
How can I parse the R tree data structure in order to infer the tree structure?   The 'tree' class has a member '$frame' which gives the splits at 
each node, but as far as I can see does not specify the daughter nodes.   Is this information accessible through the interface to class 'tree' or 
do I need to dive into the C code?

Alternatively, is there an existing add-on which does this?  I gather functions exist to read SAS code but I haven't seen anything which writes it.

Thanks in advance,

Maria