Automatically paste cells that return a value, otherwise maintain existing formula.
 

I currently recieve data dumps from various instruments runs that I
want to transfer into a master xls file. As the data varies from run
to run, I have a master file that contains all the possibilities. I
use look ups to put these runs in the right space in the master which
works okay. I want some sort of function that automatically pastes
the value (like paste special) if the cell returns a value, otherwise
if it doesn't i want it to maintain the existing formula. Any Ideas
as to how to do this?

Cameron