isothermal compressibility of hydrocarbon's condensate with Prode Properties

[cbadia]

to simulate a pipeline startup (dynamic simulation with method of characteristics) I need to calculate the Isothermal compressibility of hydrocarbon's condensate,
Prode Properties gives several options based on EOS (Peng-Robinson, Soave Redlich Kwong, CPA) and other methods as BWRS etc.
I have to solve the system for different pressures (from 0 to 120 Bar) and the values of isothermal compressibility are not constant, the software which I am utilizing accepts both a constant value or a table of values, which is the best option: keep the value of isothermal compressibility fixed or input a table of values ? How much does isothermal compressibility affect the results ?
The composition doesn't change when operating at pressures above 10 Bar while a little amount evaporates at low pressure, however the value of isothermal compressibility shows only a limited variation at low pressures.

[hans23]

possibly (for transient analysis) you need the bulk modulus,
isothermal bulk modulus is the inverse of isothermal compressibility,
with many hydrocarbons the value of isothermail compressibility and bulk modulus have limited dependence from pressure,
for example for CH4 at 100K

p 1 Bar ->0.000198 1/Bar
p 10 Bar ->0.000194 1/Bar
p 50 Bar ->0.000175 1/Bar
p 100 Bar ->0.000157 1/Bar

values calculated with Prode Properties Soave Redlick Kwong Extended
as you see from 1 to 100 bar the difference is about 20% , I think you can assume the value as constant