how to find the expression for freq in S parameter simulation?

Hi Guys
I need to find the expression for freq for further calculation. I just can not find the expression for it. I am using cadence 1.5.1 and spectre. I remembered I used to find it in browse the data, then I can find it from variable, but I just can not find it now.
Thanks

Hai
Could you explain your problem a bit more?
Which analysis you use for your circuit, what do you need to calculate.