How wide is IR-led light from VCNL4040?
It is obviously a wide angle detector (Lamertian 160 deg) with no lens, so if 2m reflection is the limit from a large white board, you must create an aperture and lens if you need to go further and block stray reflections.  But 1st you must define the range of target and reflectivity for IR and same for non-target.
So define geometry and optical parameters in order to design reflective signal and noise ratio. There are better ways if needed.