I have found a partial solution to my issue in: "Changing the case of a string with awk", the command posted by @AndersJohansson is:
echo 'ABCD EFGH IJKL MNOP QRST UVWX' | awk '{for (i=1; i<=NF; ++i) { $i=toupper(substr($i,1,1)) tolower(substr($i,2)); } print }'
Which ends printing Abcd Efgh Ijkl Mnop Qrst Uvwx, as expected.
But, in my case I have the data separated by fields, like: ABCD EFGH; IJKL MNOP; QRST UVWX
and I need to apply the command to the 3r (last) field only (actually in my data there are 9 fields, but for simplicity I put just 3).
Expected output: ABCD EFGH; IJKL MNOP; Qrst Uvwx
Inside Stackoverflow there is a good number of related questions, even one of my own (How to sort inside a cell captured by awk) , I went one by one trying to adapt them to my case without success, obviously I have not enough knowledge about awk as to overcome with the solution, so I will really appreciate any help on solving this... thanks.