VS 2010 how to select required text in rtx

hi
i have a rich text box and want to select the data that is coming form a serial port
i want to select it and then save it into a separate variable for further use

here is data sample that come from serial port

"
at+clip=1 OK

RING

+CLIP: "03365601506",129

RING

+CLIP: "03365601506",129

"
i want to select only the numeric data with in the " "
and want to save it into a variable like temp = 03365601506
plz tell me how can i select the number and filter it from the richtextbox
thanks