I have been trying to write a UDF that takes a cell range and a string
as inputs. It then checks each cell in the supplied range for the
string returning the address (i.e. $A$6) of the first instance.

I won't embarass myself by putting any of my attempts here. Finding
and selecting the cell seems easy to do as a sub-routine but I've
struggled mightily to do this as a function. I'd really appreciate any
help.