I ve already looked it up, but I really don't know how to do it. I'm looking to it for about 4 days now, so I think I put enough effort in it.
Is it this that you mean?
= CELL("address",INDEX(A1:A5,MATCH(MIN(ABS(A1:A5-15)),ABS(A1:A5-15),0)))
But I don't know how to use it in my project.