extract data from text file

[junlo]

i want extract data from "sample.txt" and save the data which have been extract to a new text file.

when have "START 129, S",then get the data below it & before the "stop"

for example:
START 129, S, 125=1;156=1;133=300000
100.05062000 3.69064000;49
STOP
START 129, S, 125=1;156=1;133=250000;93=1
100.22346000 2.88787000;43
100.18942000 2.91320000;39
STOP

data after extract is like below:
100.05062000 3.69064000;49
100.22346000 2.88787000;43
100.18942000 2.91320000;39

how to write the code?