How to pause progoram from graphical screen

I'm reading a serial port and plotting the acquired data using TKagg with the plot() command. This gives me a nice graphical screen that updates as the data arrives. What I would like to do is be able to pause the entire program occasionally as I need to make changes on the system that the RS232 is reading, then begin plotting again. Is there a way to get a pause button the TKAgg toolbar?