=VLOOKUP(C4,'Named Fields'!AH3:AM116,6,FALSE)

Hi, and thanks in advance for your help.
I have the above formula set in a workbook.
I have sheet 1 with my main information.
I have sheet 2 with all my directives.

So, I have set up as follows:

sheet 1 contains:
cell c3= client
cell c4= project
The vlookup I have entered in cell c5 is to return a job number based on the
project in cell c4 which is listed on sheet2.
Problem is, I have multiple projects named the same. They're under different
clients.
I found a post that said I could use:

=vlookup(C3&C4,'Named Fields'!AH3:AM116,6,FALSE)

But that didn't work.

Is there any way to have vlookup find what's in cell C3, then proceed to
cell C4 to returns the results in the 6th column?

Thanks,

Debbie