How to calculate speed of a BLDC motor with quadrature encoder

Hello all, 

I am trying to do speed control of a BLDC motor with a Parker MD4. I have a quadrature encoder for the motor and would like to know how to calculate the speed for the motor using the IQAN Design software. I can calculate the position of the motor from the sensor, but to estimate the speed in rpm, I need to perform differentiation of the position data. I wanted to know if there is a channel/library/block that will give speed outputs or will do differentiation? Or should I write my own Qcode for differentiation?.