pause during execution

I am trying to figure out how to pause the execution of a script and
release the R command prompt to users and then continue execution of the
script from the point it was stopped.  This operation is analogous to
the "pause" command in stata.  

If I remember correctly, insertion of a pause command in a stata script
stopped script execution and allows users to manipulate objects that
currently exist.  Upon "quiting" the script picks up where it left off.

I am sure there is such a facility, but I can't find it.

Michaell Taylor