This formula should be a little more user-friendly:

=SUBSTITUTE(SUBSTITUTE(REPLACE(A1,1,7-MATCH(1,SEARCH({"JANTXV","JANTX","JANS","JAN"},A1),),),"TR",),"T/R",)&INDEX({"JANTXV","JANTX","JANS","JAN"},MATCH(1,SEARCH({"JANTXV","JANTX","JANS","JAN"},A1),))

Unlike the last one I gave, it doesn't require ctrl+shift+enter to use.