Name CONCATENATE Problem

Hi Friends

I have Six field of Name i.e. First Name, Middle Name, third Name, Fourth Name, Fifth Name, Sixth Name.

First Name is compulsory come but the Middle Name to sixth Name is Optional


I want to CONCATENATE it like First Name and Last Name

if third Name is Blank then First Name and Forth Name
if Forth name is blank then First Name and fifth name
if Fifth name is blank then First Name and Sixth Name
if all names come then First Name and Sixth Name will Show
if third,fourth,fifth,sixth name is blank then first and Second Name will come.

For More details i attached sample file here

I wrote a custom function. I think it might do the trick