excel formula produces duplicate last names

Hey all,

I have an excel formula producing duplicate last names.

For example, I have a list like this:

Corn,Marlin
Lizand,ROBERT H 
CATANESE,SALVATORE J & OLGA M
JIMENEZ,ALEJANDRO & HILDA M
Hernara,Harry & Marie Anne Martin
CORNWALL,A ROBERT & CORNWALL,ANNA

When there is an ampersand names must get split into two columns, so i use the below formulas:

=IF( ISERROR( SEARCH("&", A15) ), IF( ISERROR( SEARCH(" ", A15) ), A15, LEFT(A15,LOOKUP(2^15,FIND(" ",A15,ROW(INDIRECT("1:"&LEN(A15)))))-1)),SUBSTITUTE(A15,MID(A15,FIND(",",A15,1)+1,FIND("&",A15,1)-FIND(",",A15,1)),""))

and:

=IF(ISERR(FIND("&",A15,1)),"",LEFT(A15,FIND("&",A15,1)-1))

This has the resulting effect:

First column:
 
 
Corn,Marlin	   
Lizand,ROBERT H	   
CATANESE, OLGA M	   
JIMENEZ, HILDA M	     
Hernara, Marie Anne Martin	   
CORNWALL, CORNWALL,ANNA	 

Second Column:   
CATANESE,SALVATORE J 	   
JIMENEZ,ALEJANDRO 	      
Hernara,Harry 	   
White,Alex 	   
Martin,Harry 	   
CORNWALL,A ROBERT

As you can see, the formula causes a duplicate of the last name in the first column. Any suggestion to refine formula so it doesn't cause that duplicate, yet doesn't negatively impact the other results?

Thanks for any response