737 envorimental envelope
 

Hi,everyone!I am operating Boeing-737 ng in one east european country.My operator has recantly started operation of this aircraft ,so there are several questions about its performance .So the question is : HOW SHOULD I USE ENVIROMENTAL ENVELOPE TO DETERMINE MINIMUM TEMPERATURE IN FLIGHT?
I know that there is special section in the AFM (Section4-p.17).But question is caused by ISA deviation and how to use in comlex temperature,isa and flight level. I will be glad to all answers.Thanks!
P.S. Sorry for my English:-)