udf for heat of reaction
 

Good day
I am using FLUENT6.3 to carry out reacting flow simulations.
I have divided my combustor into sub volumes to determine the heat of reaction by the individual volumes.
I determine the heat of reaction by volume integral of the custom field function, rate-reaction-1*((28*enthalpy-CO)+(4*enthalpy-H2)-(16*enthalpy-CH4)-(16*enthalpy-O2)), over the sub volumes.
Is it possible to do it with aid of udf?
Thank you