[How to do] Check data on cell (auto fill value)

[dungeps]

I have Range("B1:B12") and it is automatic fill value by another application (5mn/cell) and after one hour Cell B12 will fill value and after that it will clear all and start from B1 again, I want to check data on one cell until it have fill value and show messagebox and next cell until B12 and do again from B1. if it have not fill value it will check that cell again.
Plz help me how to do.
Sorry for my poor English and i hope everyone understand me .