I have 3 objects, and a custom property. I’ve set it so that when the property is set to one, object 1 has its visibility enabled, and so on. but instead of enabling one objects visibility and DISabling the two other’s visibility, it has one object with its visibility disabled, and the two OTHERS have their visibility ENabled. Heres the .blend, drivers.blend (655 KB) Take a look at the modifier tab and move around the slider, and you’ll see the problem. If you know how to fix this, that would be REALLY helpful! Thanks for reading! 
For your scripted expressions use (var==1),(var==2) and (var==3) respectively.The == checks for equality and the ( ) turns that into a 1 or 0