short answer no, waste of time. Number varibles are unlimited, and if "unknown" caller comes in, if you have customers at all, it is not feezable to block those. cells, track, throw away, it is easy to switch number CLID. If you want to script it out or to a busy or whatever with Symposium you can, before you are done, a different number from the same caller will arrive.
Mato' Was'aka