@ president
I think you are dead wrong.
Say that you took off at 38 deg with 91,3 (like I think you suggest), you would end of with a too low thrust setting.
I think you are confused.
Our FADECs sense the actual OAT and adjust the target N1 accordingly. There is no need to change the assumed temperature.
If your FADECs require you to enter the actual OAT in order to match the reduced thrust you'd get at the assumed temperature - then do it.
The OAT may change, but your calculated assumed temperature limit won't.