Record into buffer after receiving audio input

This has probably been asked before, but I couldn't find anything on the forums about it. Perhaps its my wording in my searches but whatever.

I want to start recording audio into a buffer once the audio input goes over a certain threshold. I original started by using a [snapshot~] and a [>] setting of a [record~] but the problem is, say I'm playing guitar into max, the signal is constantly over the threshold thus causing the > to constantly bang confusing the record~

I just want the recording to start i.e. be triggered once when I start playing and the recording to finish when the buffer is full.

Help appreciated!