How to apply a new temperature as a dependence on the old temperature

Hello,all
I'm a new user of liggghts and I'm studying the problem of heat transfer.
I took as a template the input file from the examples "heatTransfer_1" and it works fine with my parameters and configuration.
After that in some stage on calculation I need to heat up the particles in the special region more (to add for example 100 degrees to the existing temperature of each particle).

I guess I need to define the new variable

variable newtemp atom "temp+100"
or
variable newtemp atom "f_Temp[0]+100."

(I don't know which is right, and what to put instead of style "atom" in definition of variables in liggghts for the particles)

then I need to calculate it

compute cctemp all newtemp

To define the region
region reg sphere 0.0 0.0 0.0025 0.005 units box

and then to apply the temperature

set region reg property/atom Temp ${newtemp}

That's I could understand from the manual but it doesn't work.
How to do it right?
Thank you in advance