continuously reading two sensors (alternatively) in an event structure

Hello,

I have an event structure with various functions from user interface. The whole application is about controlling a laser diode and reading two IR light sensors which cover different wavelengths (Si and InGaAs). Both sensors are connected to the same AD converter, but to different channels. So if I want to read from both sensors I have to change the channel setting on AD converter. The real question is how to implement countinuous reading of both sensors in the event structure? I want to be able to read alternatively each sensor in a timespan of 50 or 100 ms. Is there any way, other than using timeout function of the event structure with some kind of xor logic for switching the channels? Maybe something with more functionality (somehow by a timed loop)?

Any idea is welcome.

Thanks and Regards,

Gregor Primc

P.s. The sensor reading is done by a National Instruments SPI card where SPI is the master.