quard encoder for servo

Hey, 

I have to make an encoder reader using ni daq card , in c# , my task is to read the pulses from encoder of servo drive and send the position according . I am listing my task in sequence for more clarification and also attaching the sample  picture .

1)    first i have to detect both  pulse A and Pulse b

2)  I have to compare them to see either its clockwise or anti clockwise.

3)  I have to update the counter after ever rising edge of pulse A

please help to start with it .