There is not an equivalent to the define of C language. The closest you can come is to define the conversion as a constant first (if you can) and then define your 16 bit constants as a REAL x conversion.
TRIP_TEMP : INT := REAL_TO_INT((111.5 - 32) * 5 / 9);
But I would suggest just defining the real and making the conversion during code execution using a function. Unless you are running a low power embedded system, you wouldn't notice a problem. And even in an embedded system, you probably wouldn't notice anything as most have floating point chips anyway.
In my machine programs, I mostly convert all my variables to reals first! Fieldbus values - convert to reals every PLC scan... Then I can limit my overflow/underflow errors to a small area. Plus it's much easier to debug when I see DriveTemp = 57.3 (C) instead of 573.
Famous quote: "The real problem is that programmers have spent far too much time worrying about efficiency in the wrong places and at the wrong times; premature optimization is the root of all evil (or at least most of it) in programming." Donald Knuth