VLOOKUP won't take a formula for lookup_value???

Hello,

Please see the attached (Book1) as I will be explaining my problem using this file. On Sheet1, in cell B6 I used the concatenate formula to join the two numbers in cells B3 and B4 together as one. When the cells in B10-B15 use cell B6 as the lookup_value, the cells B10-B15 show #N/A. However if I manually enter the value into cell B6 (no concatenate formula) then the values in B10-B15 show up. If I use =B3 & B4 in cell B6 to join the two numbers together, I have the same problem. I want to be able to use the "joined" number in cell B6 to look up the information for cells B10-B15.

Any suggestions?
Please let me know if I need to clarify anything.