If you are talking AutoCAD VBA, you DO NOT add reference to AutoCAD type library, AutoCAD VBA add it automatically and you CANNOT change it. See picture below: the red-circle reference is FIXED and cannot be changed:
Again, you better explain what you want to do/achieve, rather than just saying something that you should not do (adding different version of Acad reference) in AutoCAD VBA. But let me guess: you write VBA code in AutoCAD 2013 (which has Acad2013 type library referenced, of course). Then you want to a user with AutoCAD 2018 64-bit to run your VBA project and the code does not run?
If that is the case, as long as the said Acad2018 is 32-bit, your VBA project might run OK. However, who runs 32-bit AutoCAD of later versions these days? Almost no one! So, let me assume the user uses 64-bit AutoCAD (2018, or whatever). Thus, the code would most likely not work until you actually open the VBA project in AutoCAD and do some fixes, because VBA in 2013 is 32-bit. Note, depending on what the VBA project does, the required fixes vary. The point is, you need to open the VBA project in a 64-bit AutoCAD/VBA and open the "References" dialog box to fix any references flagged "Missing" and then save the VBA project. After that, the VBA project would likely work with mutiple version of AutoCAD of 64-bit without any change.