It's a bit tricky. hold(4/6) will not help you because 4/6 -> 2/3 is done by the parser. You will have to define "frozen" forms of all operators you use, e.g. mydiv:= freeze(_divide); mydiv(4, 6)
If you want to use infix notation for your "frozen" functions, you have to link them to infix operator symbols - see ?operator. If, much later, you want the computation to be done - how else could you check your work? - then apply unfreeze to your final result. You could also use hold(_divide)(4, 6) but then it is much more difficult to prevent unwanted simplifications later on. Some of the tricks explained in ?Pref::postInput may also be of interest.
