commit variables to an external program

I call an external program in background via the cmyprog.exe parameter in a custom item. Now i want to commit command-line options. Everything works fine as long as i hard-code them (e.g. cmyprog.exe arg1 arg2 arg3). But if I try to commit variables (prior responses) (e.g. cmyprog.exe <var1> <var2>) the program recieves only <var1> <var2> instead of the value (prior response). The variables are written to my responses.xls and I can use them in html-code. In html the prior responses are shown. What is wrong?

As it seems that no one can answer my initial question I want pose another one:

When will the responses get saved into the !currentsession.xls file during the experiment? (is it when i go to the next questionnaire or after the experiment is finished?) Or is there another way to access them while the experiment is running?

It would be a great help if you could provide me with an answer.
Thank you in advance.