Understanding Society User Support

Good afternoon,

I am a current researcher using the Understanding Society data and I'd like to use a few of your derived income variables. However, one variable that I'm interested in (fihhmnnet3_dv) is not present in the hhresp data file. Could you let me know how I can find this variable, or I need to construct it on my own? For reference, I am using Stata and it returns the error code r(111) when I try to use the variable.

Many thanks,
Mhairi Webster