Hi well you can use our oscilloscopes in Fast Block mode using PicoLog recorder and you can trigger the block capture on an event.
Block mode in PicoLog captures a number of samples into the memory of the device, which allows you to have fast sample rates. So more memory you have the longer you will be able to sample. This means the scope will only record the data when a trigger event happens.
Your data stream is 250kS/s , so say you need to sample 10 times as quick, this would mean 2.5MS/s and you want a period of time of 22ms, this would mean you would require a device with 55kS or more.
This would mean you would have to look at any of our 3000,4000 or 5000 series oscilloscopes.