getting mac to switch from speakers to USB headset automatically

[Jane Jordan (gmail)]

Hi, all.

I just got a USB headset with microphone to use as part of a job.  If  
I plug the headset in, I have to go to system preferences and  
manually switch the input and output to the headset.  Was wondering  
if there is a way to set this up so that I don't have to do that/   
It's a cheap set, only cost $43 at Staples.

Jane