SUBSTITUTE(ADDRESS(1,column number,4),"1","") turns a column number into a letter
SUBSTITUTE(ADDRESS(1,2,4),"1","") gives B
ADDRESS(1,column number,4) turns two values into an address
ADDRESS(1,2,4) gives B1
ADDRESS(2,1,4) gives A2
ADDRESS(2,1,1) gives $A$2
SUBSITUTE(address,"1", "") subsititutes the "1" with "", removing it.
SUBSITUTE(B1,"1", "") gives B