SubtractFrom

SubtractFrom[a, b] subtracts b from a and returns the new value.

Attributes[SubtractFrom] := {HoldFirst, Protected}

Simple examples

In[1]:= toModify = 3
Out[1]= 3

In[2]:= SubtractFrom[toModify, 2]
Out[2]= 1

In[3]:= toModify
Out[3]= 1