Dealing with blank cells with the search formula

Hi guys having a bit of a problem with the below formula,

What it is intended to do is search a customers email address to see if the customer name is contained in the domain of said email address, the name is split into three parts as seen in the formula below.

My problem is when one of the customer name cells is blank the formula evaluates as true (E-mail address okay), I've tried using ISBLANK but I can't get it to function properly that code is also displayed below.

=IF(G4="","No E-mail Address",IF(L4&K4&J4="","No Customer name on file",IF(ISNUMBER(SEARCH("@"&J4,G4)),"E-mail Address OK",IF(ISNUMBER(SEARCH("@"&K4,G4)),"E-mail Address OK",IF(ISNUMBER(SEARCH("@"&L4,$G4)),"Email Address okay",("E-mail Address NOT OK"))))))

=IF(G4="","No E-mail Address",IF(L4&K4&J4="","No Customer name on file",IF(ISBLANK*ISNUMBER(SEARCH("@"&J4,G4))),"E-mail Address OK",IF(ISBLANK(ISNUMBER(SEARCH("@"&K4,G4))),"E-mail Address OK",IF(ISBLANK(ISNUMBER(SEARCH("@"&L4,$G4))),"Email address okay",("E-mail Address NOT OK"))))))

Any advice would be very welcome!

Originally Posted by martindwilson

cant see that have you a sample workbook showing one that doesnt work?

Here's an example workbook, note the last blank cell "name 3".

In the data I'm working I can't just drop the third customer name column.