How to manipulate or use Custom Poller data values in arithmatic operations

Hi,

 

I am using NNM 8i custom poller to poll few OS related variables but i want to use the data values received in arithmatic operations.

 

For e.g. i am getting datavalue for total memory and memory used via 2 different custom pollers.Can i now use the values received somehow to calculcate memory available or %.Can i define an action somewhere so that i get my final value.

 

Please advise if you have done something similar in your environment.