need help with scheme

[Special K]

I am working on a problem in scheme (I believe you can see our textbook online - do a search for SICP; the problem is number 5.19). First of all, I need to know if there is a procedure that when called, will break out of any other currently running processes and return you to the interpreter's prompt. If such a function existed, that would make solving this problem a lot easier. I am using one right now called sleep that does something like that and allows me to test that the code works (i.e. that I can set and clear breakpoints and that execution will stop right before the nth instruction after the label and it will return me to the prompt) but the problem says that I also need to have a function that when called, will cause execution to resume after the breakpoint. As it is now, if I call the program again after it halted at a breakpoint, it just immediately halts again. Could someone help me out here?