If your table occupies columns A to C, then highlight column C and
Insert | Column so that you have a new column C. You can add the
heading CC_Empref in C1 if you like, and in C2 add this formula:

=A2&B2

and copy this down your 500 rows. Assume this sheet is called Salaries.

In your monitoring sheet, assuming you also have a Cost Centre and an
Employee ref column (assume A and B again), then you can build up your
VLOOKUP( ) formula as follows:

=VLOOKUP(A2&B2,Salaries!C$2:D$500,2,0)

and then copy this down.

Hope this helps.

Pete