What exactly are you trying to control?
Edit: Do you need to do this from a remote telephone, i.e. does it have to answer a telephone ring?
Conceptually, you will need a telephone audio transformer to couple the dial tone signal from the telephone line, a DTMF decoder circuit to detect the dial tones, and some sort of logic (probably a microcontroller) to detect a particular code sequence and perform a task. (It is also possible to detect DTMF signals directly with a microcontroller such as **broken link removed**).
Don't know that you would need any simulation software for that, unless you are performing some complex tasks.